So, the question is, what are we doing now. In my eyes the whole situation is very similar to what we have regarding H/V light signals in Germany, where there are at least 3 types all tagged the same as they have the same meaning, they just differ in how they are built.
I would think adding another subtag like ":version", ":generation", ":shape" or something for all of these cases, and then do something like
railway:signal:train_protection = nl:227b railway:signal:train_protection:shape = triangle
I turned this into a proposal in the wiki:
https://wiki.openstreetmap.org/wiki/Proposed_features/railway:signal:*:shape
Please add images of the NL signals if you have them and can share them (please also consider adding them to https://commons.wikimedia.org/wiki/ Category:Railway_signals_in_the_Netherlands).
This is a draft. I would welcome if you could come up with additional wording on the discussion page, I will transfer it to the main page then.