Hmmm. I wonder if it's because as you add skill points, the lower level recipes disappear from the vendors (which never made ANY sense to me) so if you did have a high level provisioner but didn't have a lower level green recipe you'd be at the mercy of RNG & excessive selling rates on brokers.
Honestly, recipes should appear as a player can use them and NEVER disappear unless the player has learned them.
Thanks for the info - this is bugged and we’ll get it fixed in a future patch.