I would be curious if any issue that seemed to be the size of the master cylinder was actually just a bleeding issue, or squishy brake lines. Before the new calipers could the pedal travel just as far under hard application, or was that even checked? The guy in the first video looks like he has less than new rubber lines, and there’s enough video of the line hanging, dripping that I’d question whether he’s being mindful of how hard it is to get all the air out of a master cylinder if he let it get too low.