I was trying to state the observations i had with both X type and softnose, from fast to slow calibers. You are right in that years ago, when that statement was made, bullets weren't as sophisticated as today's and also, the factory listed velocities usually were optimistic. I don't remember ever reading of an early .375 H&H account where the hunter used the 235gr. Most all were about using the 300 grain since it was normally used for big bear. Any deer/elk taken were just incidental to the bear hunt.
I read of an older Alaskan guide who liked the .375 "Weatherby" mag ( an improved .375 H&H, similar to the Ackley Improved) and he liked the 270gr, I don't remember the make. Of course, he handloaded and I'm sure he never stated it as being a meat saver, ha.
As stated, all things being equal, a tougher bullet is needed for faster velocity "if" one wants penetration,etc. My friend who used the 22-250 didn't care about bloodshot meat, he just wanted the deer to drop right there. He poached alot, I might add, and he wanted to be in and out of an area.
Americans have never been a big user of solid bullets. Africans liked ( and many still do) them to penetrate the thick skin/bones of heavier and dangerous animals. An "X type" bullet has been described as 'an expanding soild" by many. I have a Pastor friend who used his .375 H&H with 300gr TSX on leopard and elephant (head shot) Soilds are normally illegal to use on big game in America, as a rule. The only solids I have seen were for .375 and up. Some ranges won't let you shoot solids on their place. Armor Piercers are certainly not sporting rounds, but they have their place in LEO and the military of course. I had the priviledge to hunt South Africa and Namibia several times, and I always used the Barnes x or x type (Failsafe) Best of both worlds IMO ( no one is expected or required to have the same opinion as me,ha)