It's technically not an exploit as you're not tricking the game into thinking you have a lower item level, you're merely unequipping gear so you queue in at a lower item level. Now, given that higher item level = better, it should just queue you on the highest item level you can equip from your inventory (although you could just store in a retainer as a workaround there).

Now, I'm not saying it's right to do this but appreciate why people do it. Crystal Tower alliance raids, and a large chunk of ARR content in general in pretty much every queue, is a braindead zerg that saves a ton of time. I'd rather burst through CT in 15-20 minutes than spend 35-40 minutes doing Nier or Ivalice raids. Likewise, getting a level 50 ARR trial is much better than getting Zodiark normal and watching people fail to movement mechanics for 30 minutes.

I'm aware that the intended design of the roulette system is to keep players populating all queues so new players get into content as quickly as possible, but I've done a lot of this enough times already that I want to be in-and-out with no problems. We're in the raid logging territory of the expansion right now until the next tier drops, I don't want to be soft progressing content again and especially that from older expansions.