Envious makes your Silvers and Golds suck for one turn (well one Buy phase, because you can play Treasures ahead of your Buy phase with e.g. Storyteller, and not necessarily just one, because you can get another Buy phase with e.g. Villa - this game is full of edge cases).
I can accept that Envious doesn't trigger until your Buy phase, but once it triggers, isn't it persistent for "this turn", and your turn doesn't end just because you go to an Action phase? Does Envious really lose track of what turn it is if you jump to another Action phase? Or is there a time machine where you go back to the time in the turn to when you hadn't triggered Envious yet? And Envious keeps track of all of this Dr. Who stuff but I still can't Summon a Nomad Camp?
Once it triggers, it is in fact persistent for "this turn," and normally that will only include the Buy phase it triggered in, but it can include multiple Buy phases (and multiple Action phases, though it's less likely to matter there but can).
Envious makes your Silvers and Golds suck for one turn (this is inaccurate in some ways and would require way too lengthy of an explanation of edge cases to want to go into, and it turns out the ones I mentioned were already too much).
I think I misunderstood your first quote. You're saying it DOES affect two buy phases in this case. Storyteller pre-emptively avoids the treasure-sucking, but Villa happens "in the same turn after Envious triggers", so treasures still suck, further Storytellers have sucky treasures, and Return To Buy Phase still has sucky treasures.
I figured Villa should not avoid Envious, but I originally thought you were saying the opposite by mentioning it alongside Storyteller on a list of edge cases. Well, they're two weird cases, but the results are opposite. gotcha 100%.