so i’m still left in agreement, that i need to treat 𐑦 as /ɪ/ only.

I was going to try and play Devil’s advocate on this, but looking at the IPA example words you shared, I’d be inclined to write all those with 𐑰. That makes it hard to argue against this!
I wonder if there are any words pronounced with /i/ that would seem more natural with 𐑦 than 𐑰

edit and FINALLY, in QUIKSCRIPT, the revised version of Shavian, he specifies 𐑦 as ONLY /ɪ/, ‘ih.’ for me, that settles that! XD

This is really interesting, it feels a bit like we’re retracing his steps here!