Talk about BS.

There are no classes in this game. Period. Technically everyone can wear whatever he likes because everyone can meet the attribute requirements.
That's a fact.

A second fact is that more than just pure mage builds benefit from sarongs and INT. There are plenty of viable hybrid builds and even pure men-at-arms builds benefit heavily from ranking int to 8+ for basic buffs and summon spells.
If you find a sarong that's worth it then get that additional 2-3 int one way or the other and you'll still benefit.

What you said is just wrong and how are they supposed to lock/unlock itemslots for certain classes if there aren't any?