3nm is the name for node that is better than 5nm which is better than 7nm, which is better than 10nm, etc. and you can only compare it to the previous node by the same manufacturer

they literally just multiply by 0.7 and round down, so after 3nm it’s 2nm, after 2nm it’s 14A - no matter what the physical size is

it’s the name for size of the planar transistor pitch that would be required to match it, NOT the actual size of ANYTHING in the transistor and hasn’t been since finfet transistors were introduced