I find that to be the case also. A few of mine seem like they are frozen in time after their first true leaf while many are working on their third pitcher.The growth rate seems to vary a lot with the seedlings.
I've got one working on a second pitcher.
When did the trade take place?Whatever you guys are doing, it sounds like they are thriving!
I traded some of my seeds with someone claiming to have N. attenboroughii, but I haven't seen hide nor hair of anything in the mail!.
Good luck with those gems!