Ah, that makes sense. Looking at the FAQ page, it appears anyone who pays for the non subscription FSD gets the upgrade free, subscribers have to pay $1,000 for installation.
Same page says there is a camera upgrade available for some s/x/early 3s also restricted to purchasers of FSD.
All the Model 3s with v2 were offered a free upgrade, I suppose there could be some people that never bothered and then sold their car, but if it's in Tesla's resale inventory I would expect them to have done the upgrade.
My 2018 Model 3 got the upgrade and I use FSD daily, though it still has the older revision of the display (just slightly less responsive in web browsing and games).
Someone made a parser for the Google QR codes and now some apps can import them directly. I switched to aegis this weekend and it worked perfectly.