Untrue-

Fer instance, atmo is ~=340ppm CO2, but you can run yer nute much higher than 340 ppm.

The " match yer ppms" rule of thumb is meant to reduce waste- if either nute or CO2 availability becomes a limiting factor, excess of other factors becomes waste.

You won't see phytotoxicity from CO2 till ya hit about 10,000 ppm. Nute, obviously, much sooner.