not necessarily, the garand collectors mag had a feature rifle that had IH marks on the heel and springfield on the leg. seems springfield made receivers for IH.
welded receivers have a discoloration where they were welded, not to be confused with the ww2 era lead dipped heels.
This one had the discoloration and also you could see where the machining was different in the op rod channel and on the inside of the receiver behind the clip latch. I have seen other welded receivers and this one was pretty bad. It looked like it had been in a fire.
Would you happen to remember what issue of the GCA had the article on the receivers?