TColumnComboBox Flicker using themes

When using themes in Berlin 10.1 or Tokyo 10.2, and the Column Combo Box is in Dropdown mode, there is a very noticeable flicker when scrolling using the Mouse Wheel.

DoubleBuffered is enabled on the form but doesn't seem to affect this control when using Styles or Themes.

I have tested this here and compared with a regular VCL TComboBox but
1) I could not see a noticeable flicker

2) From what I see here, the painting performance of a standard VCL TComboBox is worse than a TColumnComboBox

Test project:

I prob should have gave a bit more details,   I'm using custom column colors so column 0 is clMoney width of column is 200.    The flicker is associated with the background of the dropdown being repainted white before the background color of the column is repainted on each item.    It is only noticeable when you are using the mouse wheel to scroll when the ColumnCombo is in dropdown mode.     Not sure if the background repaint of white can be suppressed when wheel scrolling as it looks like all the individual row paints will cover the entire dropdown area.   Doesn't seem to affect it as much when not using themes.   

Thanks for looking into it.