Danke!
Ich hab es auch ins Niederlandisches Community geschrieben: https://community.openstreetmap.org/t/niet-meer-bestaande-spoorlijnen/83790/24

Based on this and previous similar cases, it is likely that in cases where there's absolutely no trace left that can be used to deduce where the railway line was exactly, the ways/tags will be removed. Think of:
1. the former yard at central station (after it was dug out two years ago, it's just a grassy flat area with mostly traces of the machinery that removed the rails and moved the soil around. In a few years, a new platform + yard will be build on top)
2. Parking lot Oude Stad; road crossings without traces, places where buildings are build upon the track, and similar
3. Places where the railroad and/or it's dyke (it's a former Banndeich upon which the rail was build) has been fully replaced by a cycleway (please note that way 936498363 is misaligned now with the centerline of the cycleway; it follows the pre-2016 trajectory now). In case of good overlap, the key was:railway or razed:railway can stay on the highway, but in some cases, the railway is on what is nowadays a sloped part of the dyke (as it has shifted a bit); very unlikely to find traces that suggest the presence of a railway unless the trains ran at a 30-45 degree sideways angle over the track.

(Basically the same as that the former cycleway route, as it was before the reconstructions, isn't on the map anymore: it has been fully removed, soil has been replaced, new buildings have been build, etc.)