I feel like the Wiki currently doesn’t explain very well when to separate the carriageway vs. map a single carriage way with exclusive tram lanes.
The main motivation is that legally speaking, tramways in Germany are either street-level (i.e. embedded on the carriageway), exclusive (physically separated from the street) or independent (built more like a railway, also includes grade separated tracks). There are other rules such as legal access (e.g. cars have no lega laccess on such tracks, though busses can) and signalling (exclusive tracks need at least a Saltire for crossings, at least for highways) but for OSM, the interaction with the highway is the most relevant one.
One example I’m the most familiar is Mainzer Landstraße in Frankfurt which between Galluswarte and Mönchhofstraße is only separated by paint (which usually is considered not enough to warrant a separations on OSM) and on top of that, the only warning signs I found were some tram images on pedestrian lights but none on highway crossings — they only appeared further west. Relatedly, Heidelberger Landstraße in Darmstadt also is tagged as a dual carriageway even though some disagree with that idea and in the same city, I mapped this piece of street separately from the actual dual carriageway even though it has no physical separation up until the stop in part because of my uncertainty regarding the tram/bus lane.
On that aside, it wasn’t the first time such a discussion came up which shows that the unclear documentation is not just me.
embedded_rails also need to be updated to reflect the use of that as while it mentions legal access, it also refers to exclusive trackbeds instead of exclusive tram lanes and doesn’t cover the latter case.