Why does it say Snes and SnesClassic on the list for consoles available for smb1 speedrunning, as far as I know, all-stars isn't allowed, or is it?

You can only speedrun All-Stars Super Mario Bros. in another category (All-Stars Any% and Warpless).

So it still counts as Super Mario Bros. but in a different category.

If you click the "Misc" tab on the leaderboard, you'll find the All-Stars categories. Sometimes people miss that, but that's why those consoles are on the list.