Another angle:

Some turn restrictions on OSM are actually wrong, with same principle: they are consequential. Some irl turn restriction signs are a reminder that, due to the destination road having special restrictions (e.g. wholly bus lane), it is as if there was actually a turn restriction that prohibits e.g. turning left. This is "consequential", and should not result in a creation of a turn restriction relation; instead, map the destination path as "with special restrictions" and let the routers figure out the rest.