Afaik, they are. It’s just that third party developers would need to optimize their file sizes heavily for the great pay off of reducing their profit margin. They already didn’t want to do that for the Switch and Nintendo now enables them to not do it to incentivize more ports.

At least in Japan, I think, every 1st party game comes on the cartridge, pretty much every third party game except for Cyberpunk comes as a code.