westnordost
embedded_rails=yes is intended to be used on roads, not railways.

Or do you mean embedded=yes? There doesn't seem any documentation for this, needless to say it is not a tag I expect any software support for in any data consumer. See my last message, this tag has exactly the same issue as railway=tram_crossing etc.

I am suggesting that if the Muni Metro runs on streets, then it should be tagged as railway=tram because that is the definition of railway=tram and not following these causes problems with data consumers, as noted.

Can you link the guidelines you mention?