We tried this out last night and that does seem to be the case. I was wondering how I was sometimes able to go though hours of RP without seeing a single RP exp tick, and other times it seemed to be working properly. Using common when RPing seems to trigger the RP script properly, while speaking in Elven seems to do little, or at times, nothing at all.
When I first asked a DM about the script not working properly, I was told that the message sometimes doesn't come up, but it still banks the exp, yet whenever I would rest in these times, it would say that 'nothing has happened between your last rest and now' and seemed to make no progress whatsoever towards my next level, even though I was level 2 and 3 at the time.