I personally can readily see why the original owner tried to salvage the action. When I first became really interested in single shots about 40 years ago, there wasn't any internet and all we had was Shotgun News. Single shots in my part of the country were usually J.C.Higgins bolt-action 22s and I could count the number of locally-owned walls on the fingers of one hand. Orphan wall parts were a pipe dream down here and finding a loose receiver (or even an action with a good receiver) would have been a major miracle. Now please don't misunderstand, I've never welded-back a cracked receiver but I HAVE welded-back a number of broken tangs, ground-off hammer safety notches, extra holes and broken-off forearm retainer flange corners, and will gladly continue to do so.
It appears that in this case there was no intent to deceive anyone. My reservations in this case are because he didn't POSITIVELY ID the receiver as being broken and welded back. It would be perfectly safe with the 22RF or any other RF for that matter but the breakage & weld-back incident needs to be made plain to any future owner.
Nowadays a fairly good receiver can readily be found for a few hundred $ through the internet and so such shenanigans are largely unnecessary, but I can fully understand the impulse to try to save the part if possible. It just needs a little more work, that's all.
Regards, Joe
