I don't have figures, but anecdotally I think it's more of a probability.
Anecdotally, I'd say we tend to remember the guys who regain their previous form, especially elite players, while forgetting the guys who don't, especially less than elite players.
Even guys who have a sucecssful repair do not snap back immediately as they gain confidence in the repair and work off cobwebs. Star players, especially those with chunk of dead cap on their contract, are granted patience.
When considering a guy like Ryan, a good situational player but not a guy you'd want out there for 3 downs if it can be avoided, that kind of patience is not likely to be granted. He's a free agent. Maybe they sign him to a cheap one year prove-it deal with no guarantees for the 90 man roster. But if there is any diminshment athleticism, whether the cause is physical or mental, by the time final cut downs come, he's not likely to be around for the season.
I would similarly assess Allison's situation. While his injury was a groin muscle tear requiring surger, not an ACL, it is nonetheless serious. He's a restricted free agent. He's not a core player.
Anecdotally, I believe a lot of non-core players fall by the wayside following a serious injury with surgery, be it an ACL or otherwise.