Transparent videos don't appear transparent

[n3tman]

Things I did:

• Read Unity's Video transparency support doc, confirmed it's supported for Video Player using 2 formats: WebM/VP8 and Apple ProRes 4444

• Took this footage, confirmed that it indeed has an Alpha (in After Effects)

• saved it to .mov with "Apple ProRes 4444" codec and to .webm with WebM for Premiere codec

• also tried converting the source .mov to .webm with ffmpeg:
  ffmpeg -i colour_hearts_720p.mov -c:v libvpx -b:v 3M -auto-alt-ref 0 -pix_fmt yuva420p -metadata:s:v:0 alpha_mode="1" hearts.webm

• confirmed the resulting videos indeed have the alpha channel (imported again to AE, tried opening .webm in Chrome)

Link to converted WebM video: https://drive.google.com/file/d/1oNj2LkCbAhjnkVcP94FSSClUYUPMCPtl/view

The results:

• ProRes 4444 video appeared as glowing white: https://i.imgur.com/gSjG2EP.jpg

• both WebM videos weren't transparent: https://i.imgur.com/YZjiTiL.jpg https://i.imgur.com/amyyS4S.jpg

Positon settings I used:

[Placement]
CustomPosition = (0.0, 2.0, 2.5)
CustomRotation = (0.0, 0.0, 0.0)
CustomScale = 4

Is it possible that this can be fixed by checking Keep Alpha in Unity?

Or maybe it's caused by Glow and Lighting effects, in which case, is is possible to somehow disable them?