The circumstances of our landing in Nazjatar make Jaina's appearance there natural, she is the Lord Admiral and it's her fleet and her ship that gave chase to the Horde there.
On the other hand Tyrande suddenly being there would make little sense because she has her hands full with war in Darkshore and Ashenvale, her homeland, to take some leisurely ship trips half the globe away.
Basically it would make no sense for Tyrande to somehow appear in Nazjatar, while it makes perfect natural sense for Jaina to be there.
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Bullshit, you talk about integrity and consistency, yet you somehow want Tyrande (currently busy fighting in her bloody homeland) or hell Farondis miraculously materialize on Alliance shit giving chase to Horde in open seas?
You totally miss the context there - these Horde and Alliance fleets playing game of catch with each other had no clue they will even end up in Nazjatar. It was a complete surprise for Alliance whose mission was to basically intercept Horde fleet without any cue to why they were headed where they were headed let alone that they will end up in Nazjatar of all things.