Guardrails that break support for devices that aren't owned by the equipment manufacturer, yeah, about that…
Not sure what "support" you expect for unsupported clients.
It's definitely not true that this feature breaks support for devices not owned by the manufacturer. The follow on question about whether all possible web clients / operating systems would be supported, I don't know. The article just says that web is supported.
“Web is supported” in this instance just means “the web, but only when mediated by google, microsoft or apple”, which is not the web as far as I'm concerned.