These quests, for Alliance:
https://tbc.wowhead.com/quest=11043/building-a-better-gryphon
https://tbc.wowhead.com/quest=11044/visions-of-destruction
https://tbc.wowhead.com/quest=11045/zorus-the-judicator
and for Horde:
https://tbc.wowhead.com/quest=11046/chief-apothecary-hildagard
https://tbc.wowhead.com/quest=11047/the-apprentices-request
https://tbc.wowhead.com/quest=11048/kroghans-report
are all mutually exclusive to each other. Starting one disables the others (and, obviously completing one makes the others completely unavailable)

Version 6.3.14

Can you test with v6.3.15. I tested all Alliance ones and they show as complete in Journey after completing one.

Haven't completed one of them yet, but accepting one does not remove the two others from the map/minimap.

I have now completed Chief Apothecary Hildagard, and although the npcs of the other two quests don't offer them, Questie still shows them as available in the Journal/map/tooltips.

Now that I've reloaded Questie does consider them complete.