It's not. Forward dating was a mistake because people were trying to have the latest Porsche 911. It was more about clout and flaunting the latest fashion trend. The parts bolted on, so you could trick people into thinking you had the latest, greatest 911. The Turbo was a big factor with this. How many poorly done turbo look cars are out there?
The longhood is the prettiest of all 911s (not just my opinion, it's a wide majority opinion).
Forward dating is no "played out" in the grand scheme of how many cars are out there and how many cars you see on the road or at a show. I don't see long hoods that often. I see a lot more IB (If I see any air cooled 911s at all.) I welcome all backdates. Think about how many good backdates come on the market per year. Not that many really. There are a few high profile cars that bring big money and some midrange builds that bring solid money too. And a few unfinished projects. This ST backdate you linked is amazing. It's transcended way beyond what a 79 SC could ever be.
I'm biased, but I do think plane jane middies 100% stock and restored will be sought after. Too many were flared and molested. The low production numbers don't help the situation. My 77 targa is headed for a 100% stock restore. Should look like this when done:
It's a low production beautiful car. But it's still not as pretty as any longhood imho.