They do it a lot. My garden backs onto a public woodland and I can confirm it happens. Last summer when I tidied up out the back of my house, I found at least five years worth of buried dog turds in bags. Cleaning it up was not fun. I used a backpack blower to blow it all into line of "turd shame" away from the houses.

It looks a lot nicer out there now and I gave the trees a little prune (I'm a qualified arborist) so people know this is a "tidy area" and so far no more turds in bags.