Difference between Prune=confirm and Delete=confirm

[camaeel]

When I set Prune=confirm on one of resources, sync is blocked until this resource is gone, but I don't get "Confirm Pruning" button in the UI.
When I set any resource to Delete=confirm sync is also blocked but I see new button "Confirm Pruning". When I click it deletions happen.

I thought that Prune is a synonym for deletion of resources, but it seems it is treated differently.
Can maybe someone shed some light on this issue and explain to me what's the difference and why ArgoCD behaves like that?