Going deeper on merge feature

Hello,
I've been using DAR for many years and helped me very much. Thank you.

I’m not sure to have correctly understood the merge feature or it may not work as expected.
I’m going to tell about what’s happening.

This is my case scenario.
I'm dealing with two old archives:

-2020_full-backup
-2021_diff-backup

My goal: save storage space through merging those two old archives. 

The merged archives should contains all the files in their most updated status, except those I had deleted during the time lapse between those two backups. I don't need 2020 superseded files.

This is the command line I launched:

dar -+ merged -A 2020_full -@ 2021_diff 

The merged archive contains 2020_full backup files and 2021 new files. Changed files are stuck in 2020 version. This is the opposite of what documentation tells. Indeed, the default overwrite policy reported by docs is -/ Oo, but it seems dar doesn’t act that way considering it’s keeping the oldest version of changed files. 

So i tried to give the following:

dar -+ merged -A 2020_full -@ 2021_diff -/Oo

The merged archive is equal to 2021_diff backup archive, that’s not what I expected. dar -l output correctly tells that some files were previously deleted and all listed files are at most updated versions, but not deleted files are only mentioned and not in “Saved” status. That means I cannot restore them from the merged archive, I still need 2020_full.

Is there something going wrong? Didn't I correctly understood the merge feature?
Thank you.

--
Vash