Only native watch face has touch functions?

I'd guess that this would require Garmin IQ SDK to allow the function to the developers, and then... The developers should code that in their watchfaces! Which most of them would surely do, when allowed. Of course... Not sure if it is or it will ever be, that's for Garmin to decide

Yes probably so, I don’t se why though.

user interfaces needs to be coded - so the watch knows where to send you when you press a data field.

So just like a link on a webpage need to be specified with a destination URL - you can't just write "google" and expect the google text to take you to a google destination. 

Sure I get that, but for all of the great coders out there, I think it wouldn’t be any problems.

You seem to completely underestimate the work going into these things... Even for great coders, it's not a click of a button and a drag n drop. Especially with new devices, new features... it's a lot of work.

And again, it actually has to be made possible by garmin in their SDK (perhaps it already is, not sure... not doing much developing myself anymore).

As I have understood, Garmin release new functions to the SDK with caution (rightfully, as these can make the watches unstable), even the simple access to some data... For instance for my f6 recovery time is accessible to the stock watchfaces but not to the 3rd party ones running in the SDK. In fact, I am waiting the day when developers will be able to access this and body battery / training load to have them in the front screen, as of now still not possible to my knowledge 

No i don’t, I well aware of how it works.

And no the feature is not available for developers yet, I asked a “famous” one.

Distinct has touch. Fenix 7x ss