I understand the basic concept that a larger sensor doesn't change DOF. The change only happens when you compensate by moving close to the subject or using a closer focal length. This video would seem to confirm that: https://m.youtube.com/watch?v=ZUbU6exONdU

And yet, every DOF calculator I can find changes the results when I change the sensor size. Why? Is it because sensor size is part of the CoC formula?

And as a followup, I've tried two calculators that support teleconverters and reducers. One of them shows no difference in DOF and the other one does. Which is correct? Is it an issue of assumptions, where one calc is assuming that I'm factoring in the TC and one isn't? E.g. with a 2x TC, my 50mm is really a 100mm-- is one calculator assuming that when I say "50" I mean "50" and one is assuming when I say "50" I mean "100"?