Tryndamere ult and urgot ult interraction

It appears that there's a split second before tryndamere is completely sucked into urgot that he's able to apply his ultimate and survive (the champ models are essentially next to each other)

At no point did it seem to activate while the chains dragged him towards me, but when his model was just in front of mine, my ult animation paused, his ult activated and he survived. Does the suppression end just before the enemies are ground up? I can guarantee his ult was NOT active before I dragged him in, and from this point I simply waited out his ult out of fear of this recurring

I think Olaf is meant to be able to break it but this trynd case does not seem like a interaction that's consistent with how both ultimates work. Trynd's is damage immunity, not suppression immunity (and even then, why wouldn't it activate earlier out of panic? the ult lasts longer than the urgot animation so he would survive no matter where he activates it)

I'd assume the best way to recreate this would be to ult a trynd as urgot and have them spam R the entire time they get dragged in. I don't have someone to test that with doe