What are the implications of "asher Yipol meihem el Tocho" and "Kol Asher b'Socho", respectively?
Why must an earthenware vessel be broken? Why can one not immerse it?
Rashi: We learn from here that an earthenware vessel is not subject to Tevilah. 1
See also Rashi on Pasuk 35.
How can we learn here from a Kli Cheres is Metamei its airspace? Perhaps it merely joins its contents to be like one, like we expound (Chagigah 23b) from "Kaf Achas" (Bamidbar 7:14) that all Kelim join their contents for Kodesh!
Moshav Zekenim (Bamidbar 7:20) #1: "Kol" implies even what is suspended in its airspace.
Moshav Zekenim (Bamidbar 7:20) #2: Here it is not written like regarding Kodesh (so presumably, it is for a different reason).
Moshav Zekenim (Bamidbar 7:20) #3: Regarding Kodesh we properly expound Tziruf Kli, because the Kodesh must be in the Kli in order to become Kadosh. Here, it does not need the Kli at all.
Moshav Zekenim (Bamidbar 7:20) #4: "Tocho" excludes the inside of something else (only a Kli Cheres is Metamei in this way). If it were due to joining, we would not distinguish different kinds of Kelim.
Moshav Zekenim (Bamidbar 7:20) #5: "Tocho" excludes Toch Tocho (what is inside a Kli inside a Kli). If it were due to joining, we would not need a verse to teach that the contents of the inner and outside Kelim do not join! (R. Efrayim)
QUESTIONS ON RASHI
Rashi writes that an earthenware vessel can become Tamei only via its airspace. What is the reason?
Riva: Since it cannot become Tahor, the Torah was concerned that it not become Tamei easily 1 (through Tum'ah touching the outside).
Sefas Emes (Shelach 633): The importance of a Kli Cheres is its interior (to hold things), therefore it receives Tum'ah only from there.