I don't know about the "marked... for legal reasons" part, but there are officially surveyed road allowances all over the place that have no actual roads or have "roads" that are impassable except with the right vehicle in the right conditions.

I live in rural Saskatchewan and my work as a school bus driver and my interactions with the municipality mean that I can point out lots of bad mapping. The official bus route mapping that comes from head office always has to be amended because it seems that they do not have the data to distinguish between all-season maintained gravel, seasonally maintained dirt, unmaintained path, and road allowances that a farmer is permitted to seed or a rancher is permitted to fence off. Google and others just lump them all together when displaying or routing.