I had similar concerns using the new Material Design 3 ColorScheme.fromSeed(seedColor: Color) function.

Wanting to know the exact number of Primary colors generated, I wrote a 'Brute Force' Flutter App to walk through all 16,777,216 RBG color codes yielding only 626 total/available Primary Colors.

Material Design 3 is not a “show me every color the display can do” system; it’s a “give me a small, stable, perceptually sane, accessible, reproducible set of colors from any seed” system.

To achieve that, it fixes tone, caps chroma, uses a perceptual space, and snaps results to displayable values.

https://github.com/AndyW58/Flutter-App-Material-Design-3-Unique-Primary-Colors