So I tested this with Arathi portal and korrak summon and was unable to get my 20 into the same phase as the BFA version.
I also tried this with the warfront scenario to unlock the quest zone. Also no dice.
Best bet would be to keep trying different methods of phasing/ summoning and make sure you’re in present timeline…. But afaik, the zone and warfront is totally locked by quests that require a higher level