4th down change of possession

[Mike L]

The official case book ruling is you must move the ball so no portion of it is in the endzone. So someone gains a couple inches. No big deal. And there is quite a difference between where the officials place a dead ball and what is allowed for adjustment by the center. The line of scrimmage is set upon the ready from the R, so adjustment by the center after that does not move the line of scrimmage and therefore you still do not have the line in the endzone or, for ruling purposes, the ball in the end zone either.
What was done last year, the year before, or 50 years ago is inconsequential really. The only thing that matters is how the rules makers want us to do it now. And not having a dead ball placed in the end zone is how they want it.

oh and ps - I have never seen a dead ball placed in the end zone by the NFL or anyone else, but maybe you've been around a lot longer or my memory is for sh!t.