I will also flag that when I originally posted this thread I noted that could see that flights from NOC-LHR had availability on BA/avios every single day exactly 60 days out and not on a single day within 2 months. I just re-checked and that still seems to be the case - I can see availability on most days starting Jan 6th but not on a single day before then.

I still have no idea what is going on or whether this is intentional or not. But I am always wary of complicated explanations by call center agents in the airline/hotel industry because I've found from experience that when they don't know why something is happening, they often just make stuff up rather than admit they don't know.