Yes, it happens immediately. However, I had several instances over the years where the system made mistakes in my favors, and where the system wronged me a couple of times.
I didn't call to complained about the wronged points transactions against me, because I didn't call to return the extra points that HGVC didn't take and was supposed to take, or the extra points that HGVC refunded and not supposed to refund on a cancellation. Overall, I am out ahead, so I shouldn't complain if some more points were deducted in error than supposed to be deducted. After all, I wasn't in right when getting points I am not supposed to from before. This problem only happened on the old "Revolution" booking system.
When HGVC moved to the new booking system we use now, I did have one incident where I ended up with extra points, and about a month later, I received an email from HGVC where they said they performed an audit on my account, and noticed I had extra points, and HGVC did deduct/reverse the points out of my account. The only problem, they deducted and took out 100 points more points than they were supposed to in the reversal. That was the only time I call, so they did another audit, and admit they made a mistake in deducting/reversing too much and credited my account back the 100 points.
This is to say, even though everything is supposed to be automated and immediate, the system is not always 100% correct, probably some backend transaction problems that completed the booking but errored out on the points calculation afterwards/didn't complete fully. At least the transaction flow isn't re-calculate the points at first, and then confirm the booking. Then we may end up with points gone without any booking if the whole transaction didn't complete fully.
Moral of the story, I now check my points balance before and after each booking and calculate to make sure it's correct after each and every reservation/cancellation.
Thanks,
Great3
ETA: I went back and searched my emails and found the email I got from HGVC, last time the system made a mistake on my account was back in Aug. 2020, and they corrected manually in Sept. 2020