why shouldn't there be such a gezaira to ensure eating the korban pesach itself b'teiavon/hidur mitzva; why does the gemara specify only matza?
yl, jerusalem
See Pesachim 107b Rashbam DH O Dilma that gives 2 answers. First, that there is more appetite for meat more than bread, so Matza-bread is more likely to lose the B'teiavon, and the Gezeira is needed more for Matza.
Second, even if there is no Pesach, there still is the Matza to make for it the Gezeira.
All the best,
Reuven Weiner