For an in-depth discussion of the problem, see this section of a thread from last year: “What was previously a primary feature now became an attribute to another tag”.
For an example of the sort of code that results from this sort of change, here’s some for “is it an embassy or just a diplomatic office”. Confusingly, “office” is also referenced on the “diplomatic” wiki pages as a tag value but it’s also of course a main tag for many objects.
Another example is the change to the “amenity=charging_station” definition, as I pointed out here. I don’t disagree that there was a problem, but for a proposal to be approved that doesn’t allow data consumers to tell old-style and new-style examples seems something of an omission.
Edited 13/5/2023 to add a couple of other examples of “deprecation” issues: here and here.