First some common sense: we map tracks (railway, tram) separate from the highway elements even if in the real world they actually share the same space. The highway element in itself is an abstraction (a line representing an area). So just because those lines are crossing in OSM, they don't constitute a crossing – again they share the same space.

But it's editors like iD, that can't make sense of it, and expect something that doesn't exist in the real world. In the shared space, where tram tracks occupy the same space, there is simply no such thing as a "tram_level_crossing", that's a spam tag to make iD shut up. It doesn't improve mapping a bit.