From: Rabbi Akiva Eiger
To: Rabbi Avraham
Rabbi Akiva Eiger dismisses Rabbi Avraham's proposed resolution to the Tosfos Yom Tov's question as unnecessary, arguing the question has no foundation. He provides two independent reasons: first, the Mishnah in Shevuos has competing interpretations (Reish Lakish and Rabbi Yochanan) and thus cannot serve as a proof in Kerisus; second, even under Rabbi Yochanan's interpretation, the Mishnah addresses only self-imposed prohibitions (oaths), not automatically-arising ones like Yom Kippur, making it an insufficient source for the Gemara in Kerisus.
Source: Shu"t Rabbi Akiva Eiger §180