Are the leaderboards for this hidden in a sub-category somewhere now? Or if I submit a run should I request it be added again.

Probably ask here: https://www.speedrun.com/pokemon/forum

Don't know much about pokemon my guess is either since it's the original japanese version and there is USA release, it's pretty rare and thus no has ran it, or at some point was determined to be functionally equivalent to the american/japanese blue version. Or something.

I believe they fall under the JPN variable here: https://www.speedrun.com/pkmnredblue/full_game#Any_Glitchless

Though my understanding is Green had various differences in the game that could warrant a separate board, but that's up to the pokemon community I suppose.

I also think it's the general consensus that Green was bad and blue improved everything about it.

For Pokemon Green there only is the japanese version, so keeping up a leaderboard of that is their duty, not PSR's, who are handling main series Pokemon on here. As the japanese community is slowly shifting over here, hence the JAP language variables everywhere, they might at some point bring over Green to, until then, there won't be a leaderboard here, as far as I know