Not having used Orion or Safari much, the "allow downloads" popup is new to me.
When I visit a site to download something, I sometimes want to just download one file (say, firefox installer) and then leave. The permissions model of "allow" or "deny" is too coarse, and needs one more option "Allow this time". I don't want other mozilla downloads, just the one I am currently choosing to download this time.
This is similar to but distinct from the "don't ask when manually downloading" feedback.
A user downloading an installer from a website only want to install that particular file, so would be enabled to "Allow this time" for the one-time download permission.
As far as I can tell, Safari operates in the same way as Orion, only permitting "Allow" or "Deny".