Wouldn't Devs know about how backwards compatibility will work at this point. Surely they would need that information if they need to do a patch for a game, or need to do a full on port.
NX will probably be fully announced at least 6 months before launch.
I believe that's more than enough to patch most current titles if they go for simple up-res or up-fps.
To fully utilize the available power on existing games, it gets a lot closer to a full remake, IMO.
Devkits are probably for launch exclusives or multiplatform games not possible on OG Switch.
In which case, they may need those devkits a lot sooner.
Also, Nintendo will probably want to stagger releases, first-party or otherwise, to maximize attention and sales.
I believe NX will sell out for months no matter what. Having too many major games close to launch will only exacerbate the issue.
It would make sense to tell some third-parties to target a later release window so demand does not heavily out weight supply and to not cannibalize Nintendo's sales.
Which is why I still have hope for a launch in H1 2024.
Nintendo may want to sell their titles first on launch or close to it, probably also with titles from very close partners.
It would satisfy early demand, work out the kinks in the supply chain and they would have a very high attach rate on their games.
Then they would tell third-parties to go all out for the holiday season, when early demand is satisfied, plenty of consoles are available and Nintendo already have 2 or 3 big titles out.