You are of course quite correct, but as an empirical matter as you say COC is determined in the calculator by a lookup table, which in the DSLR world correlates generally very well with the sensor size, print size and viewing conditions are of course assumed to remain constant for the calculation too.
Perhaps dazzajl does understand what he's talking about, but the way he expressed himself it sounded like he was saying that if you keep 2,3,4 constant and switch from a 20D to a 1DsMkII that the DOF would remain constant, which is not correct. And he also doesn't seem to understand that when you crop an image and enlarge it to give the same print size you do in fact change the DOF.
As you say though, this subject has been done to death on these forums.
That's my last word on the matter, I have no desire to have THE last word here however. (Edit - And besides it's been weeks since we had a DOF thread :p )