Shalom. According to his mehalech that psul yotzei of shamnunis pasuls the dam only after kabala, the Shas could have also asked on the hava amina why is it posul if he cut the leg off after shechita?
Yzf, Toronto
This is a very important question and I will try to suggest an answer bs'd. If one looks carefully at the Zecher Yitzchok #47, one sees that he writes that immediately at the start of kabala, it is considered that "Avoda" has commenced in the entire animal. Zecher Yitzchok stresses that immediately thatkabala starts there is a psul of yotzei. According to this, we can say that this does not contradict what Rashi Zevachim, end 25b DH Shochat, writes that once the animal is slaughtered the blood of the legs become posul because of yotzei. This is because, in practical terms, the slaughtering of the animal, and the reception of its blood, are almost simultaneous. [Apart from the fact that this is fairly obvious, I would just mention that Rashi above 4a DH v'Hikreevu writes that we know that the word "v'Hikreevu" used in Vayikra 1:5 must mean kabala because it is written after shechitah. Hashomotos to Shittah Mekubetzes #5, printed at the end of the Gemara, writes that kabala takes place immediately after shechitah]. Therefore if he cut of the leg after shechitah, in practical terms this means that by the time he cut off the leg, kabala had already started. It is impossible to cut off the leg so quickly after shechita, that kabala has not yet started.
Shavua Tov
Dovid Bloom
Nu The first Rashi on 26a discusses cutting the leg between shechita and kabala - something (virtually) impossible according to your mehalech. Rashi on 25b is probably not such a problem because maybe The zecher yitzchok's vort wouldn't work in the hava amina, en hachi nami. It wouldn't be so shver to say that he's only saying the mehalech l'maskonas hashas. Which then would solve my original problem...
Very good.
I was thinking myself of answering that the Zecher Yitzchak was only speaking according to the Maskana. I saw that the Hebrew Artscrolls cites a number of Achronim, including Rashash Meilah 8b, that the Gemara changes between the Hava Amina and the Maskana. Then I had my idea about Kabala being immediately after Shechita, which I thought would make a more interesting terutz. I think it might still be possible to cut off the leg between shechitah and kabala if somebody is waiting there specially to do so immediately after the Shechitah.
Chodesh Tov
Dovid Bloom
Y"yasher kochacha. So only 68 more m'halchim to go...
Actually, the R'shash in Meilah seems to learn that l'maskana of R' Chisda amar Avimi (that he's only cutting to the bone), the gemora goes back to being m'chalek between before and after shechita, and R' Chisda b'shem Avimi only said "kibel" because of shigra d"lishna. (Notwithstanding the tertz the Shita (3) gives over here to that problem) - anyways it is already clear that the R'shash over here doesn't hold like the zecher Yitzchok because he basically asks his question and doesn't answer that way.
But we do see in the Lechem Mishna that the Rashash in Meilah quotes (Pesulai hamukdashim 1:14) that the gemora had additional kashos on the hava amina of being m'chalek between before and after shechita (he's talking about the p'sul of the animal not being kulo bifnim for shechita) and that it why the gemora doesn't go back to be m'chalek between before and after shechita, even after R' Chisda amar Avimi.
So, we could say a similar mehalech according to the zecher Yitzchok - that the gemora really had our question on the hava amina but adifa mineh porich. And l'maskana, the gemora didn't go back to being m'chalek between before and after shechita because of the vort of the Zera Yitzchok gufa.
By the way, the more I think about it, the more difficult it is to say that after shechita (virtually) automatically means the kabala started - because as long as there is dam hanefesh the kohen should still be able to do kabala, even if the first blood spilled on the floor. (I think that's correct.) So actually, it is not difficult to find a case where one could cut the leg between shechita and kabala - ie if the kohen didn't even start the kabala until after cutting the leg. - The main point being that it is very difficult to say Rashi in 25B means after kabala started.
I will just make a very short comment for the time being about the last inyan you mentioned, Reb Yaakov. Zecher Yitzchak writes that immediately at the beginning of kabala the blood becomes pasul because of yotzei. Therefore I am not sure if it would help if the kohen is mekabel the dam hanefesh later on.
Chag Matan Torah Sameach
Dovid Bloom
Again, on the last inyan. It may be that the Gemara would not want to suggest a scenario where the first blood spilled on the floor and the kohen later received the dam hanefesh because, at least according to Rashi, kabala is supposed to be very soon after shechitah. This is stated by Rashi 4a DH v'Hikreevu, according to the understanding of Shitah Mekubetzes Hashmotos #5, that I cited in my first reply; that kabala takes place immediately after shechitah. It is true that Tosfos Zevachim 13a DH Atah does not seem to agree so much with Rashi on this, but on the other hand, Tosfos Meilah 2a end DH Shochtan writes that shechitah and kabala are consecutive. For this reason Tosfos writes that it is impossible to be so precise to have shechitah right at the end of the night and kabala first thing next morning. Tosfos is saying that it is impossible to separate shechitah from kabalah.
Good Yomtov
Dovid Bloom