No, that's not it. You'll always fill up your buckets of exp to gain character levels, just as you do now, and just as in any other RPG. Let me try frame this in a different way. An extreme example, nothing like how it would actually be implemented in a game, but just to try to more clearly express what I mean.
So say you level up from 1-50 the same way as you do now. Then, instead of being level capped, you keep getting exp like you always do. You essentially keep leveling up from 50 to 90, using the same experience formula that is used when you go from 49-50. And your stats don't change at all. All this does is enable you to wear higher level gear. Keep in mind that when you're grinding for your ilvl 60 gear, you'll probably be level 60 by the time you get your first drop anyway. And when you're grinding dungeons and primals for your ilvl70 gear, you'll probably ding level 70 by the time you get your first drop anyway. Etc. Etc.
Keep in mind that this is an extreme example to try to demonstrate the meaninglessness of all these numbers, and that it is not how I would have it work in my "ideal" game design.
I'll accept your extreme example but let's take it the other way to the extreme. Let's say this is your fourth job being leveled to cap and you, being so awesome, have already bought a full set of ilvl90 myth gear for your new monk (arbitrary choice). In your scenario, that person can't equip his gear that he has worked hard for because of reasons, as it is now, he has that advantage from leveling other classes to be able to jump his monk up to a fairly high ilvl right away.