ComboBox.implicitContentWidth is not stable when implicitContentWidthPolicy is set to ComboBox.WidestTextWhenCompleted

The attached file tries to make the ComboBox narrower by explicitly calculating its implicitWidth based on the implicitContentWidth property.

In order for the ComboBox have the same width, we set this property:

 implicitContentWidthPolicy: ComboBox.WidestTextWhenCompleted

WidestTextWhenCompleted is documented to this:

The implicitContentWidth will be set to the implicit width of the the largest text for the given textRole once after component completion. This option should be used with smaller models, as it can be expensive.

However, as you can see, it's implicitContentWidth still changes while changing the current item in the ComboBox.

The ColorInputs.qml in the Color Dialog suffers from the same issue.

Reproducible with macOS style.
Can not reproduce in neither Material, Universal nor Fusion style.