Absolutely true and if a guy wanted some heavies in .358 caliber it just might be the way to go. In fact, given the success I've had with .375/9.3 sizing, I would definitely go that way in comparing & experimenting with heavy-bullets in .358 caliber if I owned a .358 Win or .35 Whelen.

The big advantage of the .375's for 9.3 shooters, at least here in my parts, is that there are a lot of .375's available, many of which are pretty inexpensive, versus a very limited supply of more expensive 9.3's. The .375's make the 9.3 a very viable "plinker" almost!

As for the benefit to .358 cal, the 9.3's offer "premium" performance, not so much inexpensive plinking or "skill-building" bullets, except for the Prvi Partizan 285, which might just be an all-round winner in the Whelen.

Your thought on the subject is right-on.