Were you objecting to "all of waze data"? Because otherwise your statement seems pretty strong without references.

Technical issues can have solutions :)

I guess someone motivated could run some experiments and try to figure out what is actually shared.

The underlying map data is the "real world", so there certainly is a mapping between the google and waze map data, even if the mapping is non-trivial :)

There are thing like OpenLR, which were invented exactly to solve these kinds of problems.