If you are asking me, I have very little opinion about it. I’ve read our wiki about it, I don’t find its level of detail (needed or wanted) to be particularly applicable to “our” present state of rail tagging (I’m USA-based in California), though I could see it being useful here if the level of detail so denoted in our wiki becomes something more Contributors want to map. Right now (at least in the USA), “not so much.” A very, very little bit, to which I have no objection, but “not very much at all.” And that’s fine.
I believe there are only 22 instances of this in the USA, a few in my Bay Area (California), Denver (Rocky Mountains urban area), Austin (capital of Texas) and Greater Boston (East Coast urban center).
As usual, “read wiki, apply what’s in the wiki to your mapping if it is applicable.” Lather, rinse, repeat.
BTW, rail mapping (between Europe — and VERY much in Germany — and USA, especially) can have significant tagging differences. These both appear to be rather widely documented (in wiki, as discussed among their “local” users / taggers / mappers) as well as understood to “work in their respective localities” without significantly harming things like routing or rendering of rail (for example, with ORM).