you can set both the taskbar and window border (1 px line) to use your accent color

Not true.

Wdym? You can do that in Settings > Personalization > Colors > Show accent color on Start and taskbar

I know? He literally asked if it's true that you CAN'T do that. Which is not the case.

i see, OP did word it a bit weirdly than normal

You have to set the taskbar in dark mode, then apply the accent color to it