The tempered Sylphs always struck me as being merely 'xenophobic'. Literally afraid of other ones. And they want all their brothers and sisters to be these ones because then they'll all be together and safe with Ramuh, their protector. Why wouldn't you want to be one of these ones, there must be something wrong with this one and these ones will correct it!
It comes with Ramuh's somewhat guarded and insular nature. He's not like any of the other primals in that the rest attack you in a furious rage over some perceived slight or because you're getting in their way. Ramuh challenges you to a duel after you have a conversation with him. He's even so kind as to wait for you to go gather up 7 allies and at no point does he make a move to temper any non-Sylph.
I kind of wish we knew more about the original summoning of Ramuh, because it almost seems to me like the Sylphs would have almost had to beg Ramuh to temper them, with the way he acted.
Of course, I could have read everything involving Ramuh incredibly wrong, that's always possible.
To contribute a bit to the original topic: I'm almost certain that the seal was not on the room but the area around Tipsumati. I seem to recall Elidibus showing up in the Solar in the Waking Sands, but I can't recall if they had freshly moved Tipsumati making it possible for him to arrive. It's been a while. If that's the case it's possible the seal existed even before the Calamity or was even created at the moment when it was used to channel the Power of the Twelve during Bahamut's rampage.
It's entirely possible that the Crystals of Light exist because the seal was made, like a physical manifestation of Hydaelyn's Will to protect a tool of the Gods from the hands of Zodiark's minions. Not that Hydaelyn reached out, picked up the crystals and made the seal, but like they were the runoff from it's creation during that moment when Aether in Eorzea was being almost literally thrown across the entire realm.