I think it's because she knows he has a talent for OPENING THINGS and will continue to investigate until he figures it out.
They are quite the team . . . when they aren't chasing each other around at full speed, or blissfully napping–each in one of the pair of wing chairs.
While Grace will
(Yep, that's a box in the second photo. I still have boxes–this one is empty, kept intact to be used for some future necessary organization . . . if I am going to fit into the limited space.)