OK, this is “fixed” per:
https://github.com/discourse/discourse/commit/3f2105db850d16a0a21db2c68bb64c4f252b7f26
I am using the term “fixed” here because it technically is Apple’s bug and I dislike contorting for them, that said, we just can’t have our “first experience” with Discourse be so flaky on a super popular device. It hurts us.
I think overall even without the existing iOS bug the experience on mobile is better, there is just almost no value in showing the “faded” page behind. That said it can probably be hacked so it’s positioned absolutely with an offset if the hack was a bit more sophisticated.
The hack applies to both IPhone and IPad.