To add on, we are also encountering the same problem with our WebGL game built in Unity. Seems like others in the Unity community are experiencing as well. So it's seemingly like this problem is effecting most WebGL experiences - which seems bad. Would be great to get some update from Apple on this.
I filed a ticket in the WebKit bug tracker here:
https://bugs.webkit.org/show_bug.cgi?id=262628
TravisChen
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Can we get confirmation from Apple that this fix only applies to iPad? We see this issue on iPhone and it's exactly what the fix seems to address.