They're almost certainly all paired with a transformer for isolation (unless maybe the whole thing is in a sealed module, but that would be rare). But it won't be a low-frequency high-loss AC transformer, it will be driven at a much higher switching frequency to minimize losses. That will also mean the core material will be different, though as I'm not a power supply designer I can't tell you the most appropriate formulation for such applications. Probably not silicon steel used for 50/60Hz AC transformers though, likely some sort of ferrite.

Basically not all transformers are equal. You need to get the properties right to match the application. In the case of their use as a component in an isolating DC-DC converter (or inverter, or other similar system) they're typically not mentioned separately, since the converter is usually a module.