Makes sense as the bodies wear as well as the stock slides, and it's not going to be perfectly uniform wear.
The slide moves rapidly back and forth with the air flow of the engine, so its always more worn fore and aft than side to side, with greatest wear pattern at front.
When the resleevers do their job they bore the body out to round.
I would guess that some bodies are so worn that squeezing to round isn't going to work.
Glen