You're results are typical of any fireforming. You will most likely see that your case necks actually shrink when fireformed, this is normal as the brass is pulled out of the neck and into the shoulder as it's blown out.
I have been running my 22-250AI with Rem brass and have not needed to trim them yet, in fact after 5 firings they still haven't reached 1.900" yet, the AI design arrests neck stretching quite considerably over standard tapered cases.
It may take another 5 firings to stretch enough to require trimming, who knows, it may even take another 10!
It really doesn't matter much, I have had no accuracy issues with the brass being different lengths by a few thou', and them being shorter even than the trim to length makes no difference to function of the brass.