This is a view that needs to be put to bed imo, it was incorrect during FCOB (When we had little choice but to stack huge quantities of SS) and it's still incorrect now.
Stacking SS will net you a little over 10th of a second off your cast. That video is a very unrealistic demonstration that's just showing what could be achieved with the right combination of buffs almost 4 years ago. I'm not even sure it'd be possible to hit the levels shown in that video anymore tbh.
It's pretty standard fare for a healer to spam stones/broils on the GCD, it's not nearly so common for a healer to spam physics/cures on the GCD.
You're suggesting that a tiny chance of saving someone in a niche situation set of circumstances (Based around a combination of entirely avoidable mistakes) makes SS a contender vs the alternatives which will help you across the board both in efficiency and general play without the need for nuanced situations to justify their worth?
Can I also add that if the timing was indeed so tight that SS would make the difference in you getting that Adlo cast off in time. The server delay would mean that the galv wouldn't have taken effect yet, TLDR: they are still dead. I haven't played much Noct or any SCH since Stormblood, but I assume the bubble delay is still approaching about half a second right? Gonna take a lot of Spell speed to make that up =(
With the boost to dots, SS is a great DPS stat, but lets not pretend it's got fantastic healing value because it doesn't.