Comment by kayodelycaon

I’m not sure. macOS has had some degree of support for touch screens internally for a very long time (2010) but required hardware specific drivers.

So this probably isn’t the matter of macOS finally adding native support. More that they revealed what was already there.

Or it can be a complete rewrite. Either way they would have to explicitly implement support for external touchscreens using a generic driver instead of a specific one for each device.