MultiEffect shadowColor cannot be used for glow

Using Qt5Compat.GraphicalEffects, it's possible to make something glow with a specific colour:

layer.effect: Glow {
    radius: 6
    samples: (radius * 2) + 1
    spread: 0.5
    color: "white"
}

When attempting to reproduce this using QtQuick.Effects' MultiEffect, the colour only appears black:

layer.effect: MultiEffect {
    autoPaddingEnabled: true
    shadowEnabled: true
    shadowBlur: 1.0
    shadowColor: "white"
}

The documentation for MultiEffect suggests that shadowColor can be used to simulate a glow effect, but this is not possible.

Here is a comparison of shadowColor as "white" (left) and "black" (right):

and the desired appearance in the Qt5Compat.GraphicalEffects' glow: