Item-Level Permission; contribute on the list item and Contribute with override List Behaviors list

I have a SharePoint online custom list, with this Item-Level permissions:-

and I defined a new permission level named "Contribute with edit all items", which mimic the built-in Contribute + this permission "Override List Behaviors", to allow the user to edit all items even the ones not created by the user:-

then i defined a unique permission for a list item, and i defined the following:-

1. I granted the user the built-in Contribute on the list item level

2. and "Contribute with edit all items" on the list level..

Where the above permission settings, allowed the user to edit the item not created by the user, even that the user has only contribute permission level on the list item level.. so is this a bug or it is the supported scenario? i mean the contribute permission should not allow the user to edit the items not created by the user, since we defined this Item-Level Permission:-

so any advice on this?