Maybe a Copy....
In 1950, Macy's didn't have the heavy nationwide presence it does today, though there was a San Francisco store. Most of its stores were in the East.
I can't see them wanting to pay the freight to ship a re-badged Western Holly product back East, all the way across the country from Western Holly's plant in Culver City, CA (not too far from another factory, Metro-Goldwyn-Mayer). These were the days when folks on the Left Coast paid different retail prices than the rest of the nation, to offset the freight factor: "Prices slightly higher West of the Rockies" was a frequently-seen phrase in ads of the day. One of Western Holly's advantages in the California market was that its pricing did not include that freight factor.
Since shoppers expected department stores' own-brand merchandise to be lower priced than national brands, I just can't see how this could have been a winning proposition for Macy's.
I am happy to stand corrected if I am wrong. God knows stranger things have happened in American retail.