What a pig -
However lets face it all record fish are freaks of nature and are not ever typcially of the species in question. While it is hard to tell from the limited picture it looks to me that the fish has been free swimming for quite some time and has grown considerably in the wild -- the fins (can't see the dorsal - darn) have all grown out and are not eroded as one would expect from a recent escapee/release from a net pen.
The body condition of that rainbow is not all that dis-similar from some of the huge browns whose picutres I have seen from the Great Lakes -- remember we are talking about a fish that appears to be of rainbow heritage rather than steelhead. It would not surprise me that it is found that the fish is of hatchery origin (aren't all Great Lakes Mykiss) that has spend most or all of its life in the wild.
Does that make it record fish? -- I would say yes.
Is it what I picture in my minds eye of "trophy" rainbow? No, for me it would be a stream fish born and reared fish of exceptional size for the given water - whether that is a 14 incher from a creek to a 8#er a large river.
Still an impressive fish!