Have I really missed that you can repeat the Legion WQ tamers all this time? I thought you could only fight them once per character, per day!
Only the Family Familiar trainers are repeatable in Broken Isles and, for some unknown reason, that does not include Durian Strongfruit.
Early on in Legion some pet battlers were upset because certain family familiar trainers were simply not appearing amongst the random 3 daily pet quests, and this was preventing them completing the achievement.
Blizzard remedied this by making most of the family familiar trainers able to be battled repeatedly, any time, by anyone.
Thank you for pointing out that Durian Strongfruit is not repeatable. I had no idea and was about to submit a bug ticket a few days ago when he was up (for just one fight)
Was also some grumbling when Blizzard made the change. They reduced the XP a carried pet was getting from the BfA WQs and at just a couple hundred XP was hardly worth doing a carry anymore. Probably a wise move now that the trainers could be repeated indefinitely.
Blizzard made the change we’re discussing years before BfA was released, and Legion trainers still give full pet XP, as well as XP for characters of any level battling them.
The one advantage BfA pet battles have is they scale, so can be battled by pets of any level.