Sorry, went to check on it but never got back around to share what I found.
The change is solely in the wording - the one that used to say something about fairly eventful now states something along the lines of "and though you haven't been entirely idle, ..."
I believe that may be a slight problem to tell you the truth. Before the recent update, I believe there were five levels of 'Activity' possible for your rest message: "Close to Nothing has happened", "Not been completely Inactive", "Fairly Eventful", "Satisfied", and "Proud". Each of these describes how active you've been fairly well, I think, but with the omission of "Fairly Eventful" it almost seems as if the xp progression has slowed immensely. Which I know it hasn't.
Also, the new "Haven't been entirely idle" message seems to be the "Not been completely inactive" message. By this I mean, My level 12 character beat down five CR8 and maybe a dozen CR3 wolves (Which he gets no xp from), rested and got that message. I've even gotten it when only smacking around a few CR5's and 6's.
So, Maybe adding in another middle-ground message would be beneficial? As it is, the messages seem to go from "You've done nothing", completely skips over moderate activity and goes straight to "Congratz! You accomplished something! Cookie?" This can be somewhat discouraging to some players as it really doesn't reflect their activity all that well and makes them feel as if they really haven't made any progress in the way of xp.
Personally, I couldn't care less if you do or not, but I believe there has been a general concern about it across the player-base about various xp-related topics. Might help to cool a few heads and make people feel a little better about their characters progression.
Just throwing it out there. I think that's what Khornite may be eluding to as well, but I'm not entirely sure. *shrugs*