Sequencer alpha over problem

I’m trying to compose two strips, an object with an alpha mesh and a background, when I do this in the compositor I get the right look:

But that’s how it looks in the sequencer also using alpha over and with the same frames:

Changing the strip from straight to premultiplied didn’t have any effect

What I’m doing wrong?

Edit:

I made a test. I created this image with some black squares with little different alpha between them and I composed the image in the compositor and also in the sequencer. The sequencer doesn’t seem to handle well these little alpha variations the first line looks the same, all black. While in the compositor you can see the little difference between the squares.

Blend file: https://drive.google.com/file/d/1LEPrFHsLEWRuwtNhrNC9NdmQgAE0KKG2/view?usp=sharing

Could this be a bug?