You're right in that Freo got the job by going in the back door, but I expect if Melbourne had tried this the response would've been "talk to my manager". Freo only had this back door available to them because they couldn't do it through Lyon's manager - if he'd responded to Freo in that manner they'd have been forced to just walk away, why would Lyon want that?
They bypassed the "process" and got the result they wanted, so well done to them there, but I think the logic of "Freo went in the back door therefore Melbourne could have too" has holes in it - the back door was only visible to them because of extenuating circumstances.