It's an interesting one. I believe the official rule is you can challenge any decision where there is a stop in play, however NRL is specific about certain issues that cannot be challenged - including forward passes, offsides, marker being square. So you would not be able to challenge the offside from a FG attempt.
What the NRL did approx 2023 was to compel the captain to name what they are challenging. So you can't challenge, for example, a high shot and then expect the Bunker to identify a knock on during the play.
The whole issue with THAT Cowboys match is that Tigers took clean possession from the kick and there was no stop in play. The referee did not make an active decision that could be challenged (you can't challenge "play on"). Cowboys should not have been allowed to make a challenge, though I am not clear if it was a clarification that was brought in later on.
But at the time, I did predict that teams would/should be challenging the final play of every match, if they have a spare call, in hopes of a Hail Mary result of guessing an infringement correctly.
Personally I think captain's challenge should be outlawed the final 5 mins, I don't like the idea of speculative challenges changing a game, e.g. a lazy head-high missed by the ref but picked up on review. I think it should be left entirely up to the ref or a bunker referral at this late stage.