Yep.
4.48 was the only size that I found consistently marked the head all the way around.
The skirt will flex back out to a larger size. No pellet we've tested, in any barrel, or any power plant, seals against the base of the grooves. What sizing can do is offer a consistency in roundness and size. If your gun doesn't like that, then it doesn't help. Sizing works in some guns, not in others.
But unless you're chasing benchrest accuracy then just getting a better batch is an easier shortcut, and even then some batches will surpassed a fettled pellet. And we are really talking about performance beyond 40 yds. At 25 they should all go through the same hole to start with.