Pretty simple question : why do MT tank suparna instead of chirada? I understand that in a full premade group it can be efficient, but with pugs, I find this pretty random.

Simple reason is that, from my experience, it's way more consistent to tank chirada. You can accurately predict the WW, and avoid feather rain. That's just less risk imo, which is important when you go with random people.
When you tank suparna+garuda, double WW can happen before the jump, OR after the jump (depending on DPS on 2nd add? this is my understanding). So if I wait the AE on the ground, then pop sentinel, it's just a bet : I can mitigate damage if dps is low, or loose the cooldown cause of teleport if dps is good, and have to use a second CD. If I wait for the jump, it's a bet and I could easily get one shoted.

I'm not trying to convince that "tanking chirada is a better method", I'm just saying that I find it more consistent for pug groups, just because it seems to me that an average group.
So I was wondering the reason why people apply this method : is it just popular even if it's not really good for pug groups (since it can be inconsistent depending on the group. Can be good for a static though), or if there is a mechanic a misunderstand there....