Reading her blog she's had issues with her wrist and a painful bone in april/may. Maybe it's not quite there yet so she isn't hitting as well as she can. But for me an even bigger reason to play a few 10/15k's get wins and confidence.
In principle Naomi has written before that she is against spending much time in 10Ks, for well argued reasons such as lazy bad habits that can be picked up while still winning, rather than challenge herself and her tennis level.
Perhaps, arguably, needs must for a few tournaments to get some matches and rythym back.