F(S)UM mean "the focus is where the mouse is"
the mouse is not on the other virtual desktop
(and it was even granted regardless of the actual geometry/position)

The "unreasonable" focus policies expose an issue about
the present linked handling of "allow activation" and
"allow raising" (see https://git.reviewboard.kde.org/r/110919/ )

Activation would match "extreme" (if the window maps on the same
virtual desktop, half a mile away from the mouse, it won't
receive the focus) but not regarding raising (which is actually
an issue entirely different from FSP)

REVIEW: 112585
CCBUG: 80897