Custom Legend Items Fill Color using series markers fillOpacity instead of fillColors

[Zordiac]

Description

I wanted to create a chart with custom legend items that are totally independent from my series. I do have two series A and B, and have set my marker Options fillOpacity to [1,0] meaning Series A shows the marker, whilst Series B's marker should be transparent. That works fine.
However, when adding custom legend items, the markers for the legend are using the series fillOpacity. I added two custom legend items with fillColors Red and Blue, but the second marker in the legend will not display, because my series B marker fillOpacity is zero. It's not a bug per se, but I don't think it is intended this way. The reason I use custom legend items is, because I want custom legend items independent of my actual series. However, it seems like they are still tied to the series.

Steps to Reproduce

See fiddle below

Expected Behavior

Legend shows to markers with red and blue

Actual Behavior

Legend shows 1 marker in red, and the other one transparent

Screenshots

Reproduction Link

https://jsfiddle.net/b6vh27ka/

You can see the second marker in the legend in blue not displaying