Seems like Apple has not yet implemented RFC7616 (from 2015) in Safari. Of other browsers, Chrome gained support for it last, in 2023.
Apple rules don’t allow other browser engines on iOS, so for example Firefox on iOS uses Apple’s WebKit, instead of their own Gecko engine.
Safari on macOS also fails, while Opera/Firefox/etc work on macOS. Since there is no such restriction on macOS.
Chrome on Android works fine too.