Quite frankly, in my experience the current levels as defined by the administration if off-par from what people associate with personally. The one exception is probably free. What do we see in free? A lot of one liners, a lot of illogical nonsense, and what not. Perfectly fine for a lot of people and especially beginners. Casual is also okay listed where it is at. Low Casual perhaps requiring a few coherent sentences that are somewhat related to a mid-depth character at hand. Casual itself having the pre-understood requirements and high-casual being for all extensive purposes advanced. 

In my experience over the years, most advanced threads require a post of no less than one page anyway. Of course this is not because of some explicit requirement but the understood conception of what an "advanced" role play entails requires it. The important thing to understand about the distinctions between the three models is that post size is relative to the players. However, it is the quality of writing not the quantity in which I believe truly dictates the level of role play. Free role play might as well be l33t speak or all joking aside, grammatical gibberish that is about as deep as a puddle as most characters may be static in nature.. Casual role play requires a better grasp of the English language and with characters perhaps trapped somewhere in limbo between static and dynamic. Interactions may be based more around the characters as created rather than the players personal experience as with free. Finally, we have the advanced level which truly requires a more dynamic character role as well as a sense of understanding with regards to the setting. Personally, I have always found the advanced role playing section a little problematic because the posts between characters don't necessarily flow in a matter in which one might assume would be advanced. It really ends up being "high casual" on steroids. 

So overall, I think it just happens to be that the Guild's definitions of the levels might be a little outdated rather than the players misuse of terms or what have you.