[tehlike]

My suspicion, having worked at google for a while, is that this is a parser / version eligibility bug. Someone probably put the list of major versions where this is supported, and 15 was not there :)

Things like this happened every new ios release. Going from 9->10 was a problem for example because regex used was limiting major version to single digit etc.

[LynxInLA]

Except AMP links were showing up in iOS 15 in the beta and for the first few days after official launch.

[SimeVidas]

There could also be a newly discovered bug or change in Safari 15 that affects AMP pages.

[mobilio]

Also AMP it's disabled for Firefox on Mobile (Android)