All my NG+ gear has 8 levels higher requirements as well, but have figured it's because I started NG+ as level 38, which is 8 higher than the minimum NG+ level of 30.
Also a few times when items have been automatically unequipped (like when "training" with Rosa var Attre) I've been unable to re-equip them afterwards because their required levels have risen to higher than Geralt's level.
Interestingly enough it doesn't happen with all gear: happened with the Temerian armor and legendary Viper swords, but didn't when I loaded an earlier save and equipped different, random gear from my inventory before the automatic unequip occurred.