cache exports image twice

[ktomaszx]

Hello,
I'm wondering what is the reason that command:
docker buildx bake --file planned-docker-bake.json --push
exports cache to ECR twice. One is tagged and the other one non tagged. The have the same size in ECR repository.
docker-bake.json contains
"cache-to": [ "type=registry,ref=***.amazonaws.com/cache:dependency1:tag12345,mode=min,image-manifest=true,oci-mediatypes=true" ]
In logs I can see:
Exporting cache to registry twice:

and

and then in ecr repository I can find two images one with proper tag and second one (same size) untagged like below

In exporting logs I noticed that writing config sha is different and then of course cache image manifest are different. Rest sha of layers are the same.
Probably this is desired behavior and I don't know something.
Interesting thing is that it doesn't always generate two images but hard to say what it depends on.