AE renders RGBA with layer motion blur including background color of comp

Issue: RGBA *.mov rendered motion blur including compositon bg color.
Versions: AE 23.2.1, MacOS 12.3.1
Steps to reproduce: Make an animatin in a precomp. Place precomp in main comp. Activate "motion blur" for precomp layer. Render "logo reveal.mov" RGBA . AE main comp had a green background color, so i can see the animation. Imported "logo reveal.mov" in PR. Animation has green gradient around the blury edges. I expeced it to be blurred from solid color to transparent, not including any color from AE comp bg.

^ Logo reveal comp AE

^ Logo reveal.mov (RGBA) in PR