
Originally Posted by
Vickii
I think comes down to <spoilers>
It's more than just that, though. (More spoilers, this time all the way through 5.3.)
The ShB storyline actually will acknowledge if you haven't met G'raha Tia yet from your standpoint, but to explain some of his motives and reactions he does need to know and have worked with the Warrior of Light at some point beforehand in his personal timeline. So they wrote the dialogue there as though you hadn't met him yet.
However, the 5.3 MSQ ends with bringing G'raha Tia home. For the sake of the writers' sanity (and Timeline Shenanigans in general), that means you need to have met him before that happens (and he needs to already be within the Tower), which means you need to have gone through those alliance raids and completed that storyline before that part of the story occurs. Trying to make divergent stories for people who never did those raids would probably have been a maddening process.
That's almost certainly why it's a requirement to have finished the Crystal Tower raids to even start the 5.3 portion of the MSQ, even if you had gotten to 5.2 endgame without ever doing those alliance raids.
I suspect adding them as an MSQ requirement on the way to Heavensward is just a way of slipping it in as content you'll do when it's at least somewhat level-appropriate.