Report theme not working with custom visuals

Hey there!

I developed my custom visual with custom design options but actually I am not being able of changing this options by using PBI Report Themes. When using a native visual I don't have any problem.

I made a really small demo for you to be able to see the problem by yourself: https://drive.google.com/file/d/1AwryId1uPe2pp7XnnGbS5NpcPLdbwdnl/view?usp=sharing

Am I doing something wrong? Is this a bug? A feature? Any advice?