Is it a bug that I can't get alpha for H265 mp4?

I saw this blog post and learned that even mp4 can have an alpha channel if it is h265.

So I made an mp4h265 video with alpha channel and set it to opacityTexture but the alpha part is black.

Is this a bug in Babylonjs?

AFAIK H265 is not really supported. caniuse shows this:

HEVC/H.265 video format | Can I use… Support tables for HTML5, CSS3, etc
If you want to reproduce this on the playground we will be able to check it, but if the browser can’t decode the video correctly there is little we can do