Breeze has
if (!(widget->testAttribute(Qt::WA_WState_Created) ||
widget->internalWinId()))
KWindowSystem::blur(widget->winId(), ...)
which makes sense as the style should not be creating surfaces in polish
and I don't want to remove it.
This is problematic with QMenu::polish which has a subtle behavioural
change compared to QMenu::exec in that it calls ensurePolish before
creating the surface.
Plasma::ContainmentInterface accidentally has this workaround already
for parent window setting.
BUG: 395262