I want to mention that my learning partner, David Bronson would not have left that 2nd Tosphot on page 18B of Bava Batra unless he understood it fully. And yet I tend to go along with the approach of Rav Nachman of Breslov in learning “to say the words in order and then to go on” in learning Torah and Math and Physics. (And then later to review and Izhak Rosten once told me. I.e. even with this approach of “just saying the words”, it Is very important to later to do review until you get the idea thoroughly) .. That was definitely not the approach of David Bronson. However, it could be that if I can try understand the great Rav Shach and Reb Aaron Kotler on this subject, perhaps I can answer that later question I was asking on that Tosphot, (i.e., “why he changes the original assumption) .Obviously Tosphot himself was worried about this difficulty and tried to answer it, but I still cannot see how their answer helps. It possible that because of this problem that Tosphot himself in the third Tosphot on that page decided to start looking at the approach of Rabbainu Tam and Rabbainu Chanaanel. {I think at least for me, I will not be able to understand rabbainu Tamuntil I get that second Tosphot approach of Rabbainu Izhak}