I think it is more of an underbore-vs-overbore issue.
In theory, a higher pressure round that delivers a given level of projectile velocity will have lower pressure, cooler gas than a lower pressure round delivering the same performance. In essence, the higher initial pressure results in more of the energy being extracted as mechanical energy...leaving less in the hot gasses behind the projectile.
The issue is confounded. The technology of smokeless powder and metallurgy co-evolved. The 30-30 was the knife's edge of how much smokeless powder you could stuff into a cartridge given the powder and steel of the day. Things proceeded rapidly from there.
Consequently, it is hard to find an modern, underbore round that is loaded to high peak pressures.
One experiment would be to compare a .308 Winchester 150 grain load with a .300 Rem Ultra Mag delivering the same velocity with the same powder (say H-4895). The .308 would likely have higher peak pressures and milder shooting characteristics.
