Yeah it is, I’ve got three of those 18650’s from Provape and they all are just a tad short. They still fire perfect just not as tight as they should be. It really doesn’t matter though because like you I love the 18350 mode. Only thing is when it’s in short mode and in my pocket it’s harder to keep it upright.
Hmmm have you locked the switch to determine if it's the switch rattling and not the batt. I say that because before I went to magnets my switch rattled but the batt fit without any movement. I had to tighten the locking switch to determine the source of the rattle and it indeed was the switch and not the batt.