This is a good example of why crossing=* is so bad. There’s 3233 features (Overpass Turbo) with crossing=unmarked + crossing:markings=zebra which is nonsense.
If we tag the objectively observable features on the ground, any region can work out what it means for them based on the combination of:
crossing:markings=*
crossing:signals=* (ideally extended with =shared|dedicated (proposed))
crossing:signed=* (proposed)