chock-a-block Does this hardware exist in previous Pixel models or is this only possible on the 8?
I think other manufacturers have shipped phones with DisplayPort (Samsung?), but I believe no Pixel before the 8 had DisplayPort. For example: https://discuss.grapheneos.org/d/1178
With respect to a desktop mode in GrapheneOS, at present this is hypothetical. Exactly what the Pixel 8 hardware is capable of is still not clear, and it does not seem as if Google has released desktop code for phones into AOSP so far.
Personally I suspect that, given the large number of regressions in AOSP Android 14, and given that Google has yanked some widely-rumored features from A14 (e.g., app cloning), some features may roll out in quarterly releases. If so, it may well happen that not all of the eventual A14 features make the next quarterly release.