That sounds like a logical explanation to me.
I personally assumed,right or wrong, LMT changed that dimension to allow room for funk that accumulates in the barrel extension/breech face of the barrel.Like you, Im sure, have seen that area look like the bottom of a gold fish pond in short order,so that also makes alot sense to me.
Never had a bolt fit tight in a barrel extension,to date,so haven't experienced that yet.
Also with the .272" lug length, the bolt lug face is nearly flush with the front of the extractor claw,eliminates the edges of the bolts extractor channel at the bolt lug face, making a more consistent,smooth surface, IMHO.
Regardless, Ive seen no issues,so it must be a fix for something or LMT wouldn't do it so precisely.

