You may be putting too fine a point on the dimensions of Advanced, to begin with.

"But Ruby, Advanced means a page of wordy-jibba-jabba, at least!"

Yeah, no. It means an Editor wouldn't kick your RP's IC out of bed. Plot, setting, pace, even a little bit of art. (What some may call 'fluff' or 'padding' posts.)

Now contrast that with the Casual rundown.

Not TOO far off. More focus on the interactions, the characters, maybe setting, definitely storytelling. But there's no pressure to be novella worthy. But there are no RP police that come and put a black bag over your thread and hurry it away into the night if it says 'High Casual' but doesn't...whatever; met a length requirement, doesn't focus enough on storytelling, doesn't establish enough setting, or pace, or mood. 

It's subjective. 'High Casual' is as much a declaration of RP intent more than it is a unit of measurement. If the observation is that it's 'over used'...well, maybe. But, again, it's subjective. To me? Yay it's being overused! They're all, Free/Cas/Adv, just guide lines anyway. =)