No, and why? Because outright anti-consumer shit like that tends to leak. And if it did that would be very bad for Nvidia. Just look at the backlash Blizzard got for the Taiwan debacle or how costly it got for Google in the Epic vs Google case just recently. It's much much better to not rock the boat and go with the route of just not spending the (small) effort on making the feature work on the older cards. At the end of the day Nvidia has what? 90% market share in PC GPUs? Even though AMD is trying to be the more consumer friendly company they're not getting any results from that approach. Hell if we disregard ray tracing AMD has given significantly more FPS / $ for a looooong time without that mattering to the majority of consumers. Hell even Nvidia cards that can't really deliver decent ray tracing like the 3060 absolutely crushed AMD in sales numbers.

In the end Nvidia doesn't need to do shit but not fuck this up for themselves. Their only competitor in reality is their older cards so by not porting the cool new stuff to them they get more new cards sold. People getting FSR3 working on the old cards via hacks is a threat that is vastly smaller than the threat of bad PR if they had a strategy to outright block stuff that could benefit their older cards.

EDIT:

I wanted to add that if this was someone getting Nvidia DLSS3 Frame Generation working on the older cards then it would result in screaming internally and a sign that they kinda suck at their job. But this is FSR3 and a very unstable hack at that. It's technically impressive that they got it to work but not a real threat to Nvidia bottom line. At worst a couple hundred techy dudes don't upgrade as early because this hack holds them over a year or two. Big woop. It's not something Joe random is going to run or tinker with.