I had read that UK teenagers say "scun" for the edible.

I don’t know about this suggestion, Dr Bill. It's certainly new to me. Most UK teenagers probably don’t eat scones - they have a rather old fashioned image! It is possible that somewhere in the British Isles the word is pronounced ‘scun’ in the local dialect but I haven’t found anyone that has heard it pronounced that way. The word is Scottish, but the Scots and people from the north of England that I have asked would say, approximately, ‘skonn’, not ‘skunn’ and not 'skawn'.

There is a word, ‘scunner’- it has had the distinction of being a wwftd and I can do no better than to quote from that august source:

"scunner - [Scot, v] to be in a state of disgusted irritation."

So, there is no connection between ‘scone’ and ‘scunner’.

As a by-product of this enquiry:
The Stone of Scone (pronounced ‘Skoon’) is named after a location close to Perth in Scotland and, as you know, has no connection with scones to eat! The mound at Scone where the Scottish kings were crowned has had many different names one of which was Boot Hill – which came from an ancient tradition whereby emissaries swore fealty to their king by wearing the earth of their own lands in their foot-bindings or boots.
So not all Boot Hills were to be found in the wild, wild west!