Definitely not a carpenter bee hole. Carpenter bees make much smaller
and neater entrance holes, perfectly round, about a 1/2" diameter,
just large enough to admit the bee.... deeper inside they excavate
galleries and chambers.

Woodpeckers don't make holes like that either, they need a much larger
diameter to make a deep hole... woodpeckers nest in vertical wood and
much higher.

That hole looks like it was made by some other insect, probably some
sort of large beetle... looks more like an exit hole, the insect
pupated and chewed it's way out. Insect eggs were laid on the
surface, upon hatching the "worm" chewed a tiny diameter hole deep
into the wood where it created a chamber, now after pupating it made a
much larger and messier hole for its escape.


That is one HUGE insect! Well, it certainly made a larger and messier hole