Yeah, the elephant in the room reference caught me as well, although from memory, a line similar to that appeared towards the beginning of the Patagonia special as well, so it could be a mere coincidence.
To be honest, I always anticipated series 22 to be the last series (with the three of them anyway) based purely on the content within it. The Patagonia special was just crammed full of tiny little nods here and there, the St. Petersburg race, the ambulance challenge, along with the two film shown tonight all feel like the more classic TG challenges only with a bigger budget - mainly because that's what they are. But as you mentioned, they still manage to somehow slyly call back to some older episodes, and I can't help feel there was some intentional merit behind that.