I believe the piles stuck together is from a more consistant diet of succulant "green" browse.
Kind of like, when you eat a whole big bag of grapes and the next day your poop is much looser. Man I hate that!
If you think back to later fall, after a few frosts, apples and other "green" folliage dissappear and the droppings turn harder due to harder browse in the Deer's diet,
like acorns, twiggs, etc... as there is not much water in this type of food.

As for the size of the pebbles, I personally can't really say one way or the other???
However, I have recently read an article "claiming" that the bigger pebbles are supposidely mature Does,
but common-sense tells me that, the bigger the Deer, the bigger the poop!
For what it's worth??

Maybe you could set-up a camera to check?