By now, I believe we have a few years’ worth of evidence that end user applications often won’t get the distinction right if you leave it to sub-tags. Some developer will rush to build an app in time for the deadline, see that all the walking paths in their urban surroundings look great if they apply this or that render style to highway=path, and have no idea that this causes scrambles to be displayed in a way that misleads their app’s users into dangerous behavior.
It’s generally safer to design in such a way that imperfect humans will tend to do the right thing by default. That’s more effective than warning labels telling them not to take the seemingly obvious approach.