Artifact +Spell Gem Slots

Because I’m being hyper aware of the my spell gems right now because of my previous post I just noticed something else that happened. My level 50 Sword has pump drill giving it additional spell gem slots. For a while it was giving me 4 spell gem slots but now it is giving 3. Comparing to my level 45 artifact that gives 2 the 3 at 50 feels right but its just weird that it happened at all. Not sure I would have even noticed if I wasn’t making sure my spell gems weren’t mysteriously disappearing.