Some good news and some bad news...
The good news is that I'm getting a response from the APIs again, but that has more to do with some changes my ISP has done today rather that GOG lifting the block, as far as I'm aware. Of course, now I have no way of checking how long a block lasts unless I get blocked again :|.
The bad news is that there is indeed a throttling/blocking mechanism now in place on the products API at least. With some help from a friend that has some AWS instances and doesn't care if his IPs are blocked by GOG or not, I've determined that the throttling is global, his IPs also being banned after various time intervals in which the scanning script worked fine.
The conditions triggering a block seem to be erratic... perhaps there's a schizophrenic machine learning algorithm that controls things without a discernible pattern, or perhaps GOG has trained monkeys for this task as well.
I'm still trying to figure out how to avoid triggering a block, either by lowering the scan rate and distributing the load across a number of IPs or by offering the monkeys responsible for blocking some tasty bananas.
All things considered, I'm getting closer to ending a full mapping run, now a little above 2 billion ids mapped. Nothing spectacular or worthy of mention in the latest batch.