Yes, yes, yes! After I posted this I thought, nobody is going to understand this one.
Thanks, mommaandmore and others. Your descriptions have hit the mark. I do think some of it is boredom; and some of it might be trying to check out things they can sort of intellectually 'get', but don't have the motor skills to deal with (rip, tear, shred).
DH and I will sometimes look up from reading, eating, whatever, and have one of those 'It's quiet. Too quiet.' moments.
One time I came into the dining room after literally only 4 minutes of being out and dd (1 at the time) had completely covered the dining room table with a pretty even coat of milk and cereal. And a good part of the floor. It was remarkable in both size and consistency - like she had been evening it out here and there...
Then there was the time she pulled out the noise-maker in a toy of ds's, she's completely shredded many books, and so on.
I think the books definitely end up in the category of 'oh, here's some cool stuff that I'd never see in a board book so let's check it out.' Then 'darn I've torn the page, wait...THIS PAPER REALLY SOUNDS COOL WHEN YOU TEAR IT!! '.
Asynchronous dev.?
Oh, and btw, we try to fit into the 'put that toy away before you take out another' camp, but it just does not seem to happen...we just sort of get out the bulldozers once a week and 'reset'.