Sounds like bullshit has replaced a once useful physical measurement. They should've found a new, real and objective measurement or just given up and used a date or arbitrary version scheme.
The shape and construction of the gates and transistors changed. Minimum feature size ceased to correlate with density/performance in some senses. This scheme has been somewhat arbitrary since about 20nm or so afaik, but expectations are set around what the number communicates, so here we are.