This is probably breaking my NDA to say this, but yes, they did. Web.app now has the "dynamic-codesigning" entitlement, which enables Nitro.

What about UIWebViews? I believe I've read that they do not yet gain the Nitro benefits.

They don't, but that's a security restriction. They can't give dynamic-codesigning to all apps, or their security (which that disables, as a requirement to enable the JIT) would then be useless.

Whilst the lack of that feature certainly wasn't good, how can that be described as a 'bug'? Nothing was broken.

Surely the same page running on the same browser on the same device but with 2 different javascript engines depending on where the page was launched from can best be described as a bug. A design bug, perhaps, but a bug.

Home screen apps are not running in the browser - they run in a separate process.

What distinguishes a 'design bug' from 'doesn't work the way I want it to'?