Summary:
Many games see noticeable improvements, but how much of an improvement will vary. Games that are bottlenecked by GPU or memory bandwidth benefit significantly, whereas CPU-bound titles only see small improvements.
Arkham Knight, famously one of the Switch’s worst ports, is now a playable 30fps. Dragon Quest Builders 2 is… playable but still not great, building as much as possible to stress test the hardware can drop to single digit framerates on Switch 1, that’s now around ~20-22fps here. These are the two most demanding titles tested, which means that most everything else came out pretty good.
The obvious caveat here is that games cannot exceed hardcoded targets. Games with uncapped framerates and dynamic resolution will be able to take advantage, but capped framerates and fixed resolutions must remain so.
I think it’s because the market changed around them. When the 3DS launched they were one of the only companies providing decent BC. Now, everyone does it and people expect games to actually play better on the new devices.
Still a surprise that Nintendo got the message, but with the dozen first party games that got free patches it was clear this was a new era for them. I’m playing Pokemon Violet right now after beating Scarlet a few years ago and it’s like a whole new game on Switch 2, all the performance issues are just gone.