For instance, does it mean they can measure RF voltages without an RF probe??
Yes............. But........... I have an HP 3400A similar to this:
It's the FET equivalent of an AC VTVM that's good up through 10 MC's. The input connector is a BNC as it's used with a shielded scope probe, not a pair of test leads as the Heath
kit would typically be used. That's an important distinction as the HP has two additional ranges and is 10x more sensitive than the Heath
kit. Stick a short wire in the BNC center pin and it will bounce the needle in sync with the strongest AM station in the neighborhood. An AC meter is most commonly used for audio work measuring levels through a mixer / patch field / distribution amplifier, etc. but is also useful in alignment work. It can measure levels in an AM or FM (10.7 MC) IF amplifier very accurately or show a clean null. Personally I prefer using a scope as the absolute level doesn't matter as much as finding the alignment peak, but for something like an FCC commercial transmitter proof it's the numbers that matter.