Since Skyrim? I’d say their quality has been slowly declining since Morrowind. It wasn’t that noticeable at first, since oblivion, fallout 3, and Skyrim were still quite good and fallout 4 was decent. But then fallout 76 was a mess at release, TES blades was shit, and starfield just seems lazy.
The number has some connection to transistor density, in the sense that a lower number means generally higher density. However there is not any physical feature on the chip that is actually 3nm in length.
This has been true since the late 90s probably.