The conspiracy theorist in me suspects that Intel must be applying heavy-handed pressure to OEMs to keep them in line long enough for Intel to release a better architecture in a couple of years.

The realist in me says that AMD has had major supply issues delivering the 7nm Zen3 chips in any appreciable quantity while Intel literally prints 14nm chips like it's going out of style.

Given that you can spec a comparable Ryzen vs. Intel system on Dell's site I'm thinking Dell is just prioritizing their marketing focus on the systems where they can move the most volume. Else they'd be shooting themselves in the foot with "SOLD OUT" notices and backlogs.