I can’t prove it either but can guarantee they haven’t released any seats during that period. As soon as they came on sale and redemptions became available, I was checking, and have checked religiously daily (sometimes multiple) - and they did come up for prior days, up until then - and then not for that whole period.
I had a similar experience
here on blackouts for the week of US Thanksgiving (puzzling for a SIN-HKG flight?). Abundant availability that abruptly stopped across all classes. I've been monitoring those Nov 2025 dates daily and nothing at all has appeared (except for that brief glitch a few months back, but I couldn't get a booking confirmed).