Ah, that is because the .375 is a non-bottleneck cartridge typically used with flat based bullets that will vary in diameter depending on construction (jacketed vs. cast) while the .30-06 is more often reloaded with jacketed bullets whose diameter will be a consistent .308". An expanding die is included with die sets for cartridges like that while bottleneck dies typically do not include an expanding die as they're often not needed unless you're loading cast bullets. And yes, some inside chamferring is all you need. The .30-06 seating die (Lee dead length seating die) is not a crimping die, it has a portion that stands the bullet up better than a roll crimp die to align the bullet with the case mouth. They work good with flat based bullets and tend to eliminate crushed cases and egged out case necks.