Strange then that I can walk in to dealers & find a selection of .20 pellets or even slugs in 3 different weights

just because there are 50+ types of .177/.22 pellet who actually buys/keeps more than the half dozen regular suspects ?

I've got 6 different lead & 4 lead free in .22, 6 different lead in .20, & 5 lead & 1 lead free in .25, & I don't even use all of them because I know which pellet is most accurate in which rifle
no .177 because I don't shoot paper

Depending which .20 rifle I choose I know I can shoot a magazine of either FTT, JSB exact or Predator Polymags in to a ragged single hole group at 25yds, so accuracy is fine.