I agree that one should try to match one's stats to what one RPs. However, I don't think that it is possible to achieve this most of the time, at least in the current state of PS. There are the unimplemented things for one thing, and there also is the problem that even for the implemented things, there still tends to be need to fight. Otherwise, you don't get XP and money nearly as fast to make it even (and things are often being changed as well). Plus, and this is independant of the state PS is in, you usually don't get that much chance to RP what you level.
This is something that makes me wonder if levelling is the correct approach to RP at all. Just consider the ridiculous speed at which people can gain levels if they focus on it. Even if we were going by the insanely fast ingame clock, they go from peasant to master fighter in a few months. They get insanely rich in the process as well. Seriously, this is nowhere near realistic, and therefore it is impossible to RP it. Hence, even if you veil this into some sort of "My char is obsessed with becoming the best warrior" pseudo-RP explanation, it's not RP regardless of how you phrase it.
Thus, either you start pretending that you already are a master warrior right from the CC (with a gross mismatch in lvl vs. RP), or you have to significantly reduce your levelling speed.
IMO, players should have no influence on the levelling speed of their characters, and only get to pick the skills to level.
What makes matters worse is that PL (even if veiled in RP terms) effectively devaluates skill levels. This means that a PL increases the threshold for what must be considered "high level". Someone who RPs "a good warrior" will therefore have to kep on levelling in order to maintain their effective level, even if they never RP an increase in skill.
For all those reasons I view it as mandatory to RP consistently, realistically and believably, but matching stats to the RP is something that can be omitted or at least delayed. I, for one, am not willing to put up with days of grinding just to increase some stat, eg. END, to what I RP, especially not after a wipe. If anything, I do it gradually, when I have nothing better to do because, frankly, for most characters grinding is totally OOC. It has taken me about one year to stat-wise approach what I RP, even though I by far don't RP high levels, and none of the grinding could be done IC.
Of course, if you are not sure about your ability to maintain consistent and reasonable RP, then it is better to use the stats for guidance. However, as stated, the stats themselves can easily lead to and support god-moding (For example, I don't think Ulbernauts can realistically be killed by a lone fighter, and therefore have severe doubts about the RP quality of those who "kill Ulbers for fun").
All in all, PS should significantly reduce the reliance on skills and stats, and instead actually focus on RP (meaning flexibility in what to do and how to do it, extensive interaction with the environment, visuals, etc., not merely hiding information).