[Ajedi32]

Actually that's not true anymore, PD Revision 3.1 has an adjustable voltage supply mode that can do any intermediate voltage between 15-48v, with a maximum power of 240W: https://www.usb.org/usb-charger-pd

I don't know how widespread support for that is though.

[omgtehlion]

PD2.0 is here for a decade already, yet many power bricks skip steps between 5v and 20v, so I wouldn't hold my breath here...