From the FCC's point of view, performing any denial of service attack on a radio channel using either old fashioned jamming or other technological means is illegal. It doesn't have to distinguish between the two because the intent and end result are the same.
What about using bandwidth to the extent that it degrades performance for other users? Is using 80Mhz for my wifi for my legitimate use-cases in my apartment while copying lots of photos to my NAS and thus using up most of that an attack? It would measurably degrade the performance of nearby wifi, and given a location in an apartment and my naive default power levels of "everything to max" (as most wifi routers operate by default)...
Why is everyone in an apartment who isn't a radio engineer guilty of interference given the broad definition? I know that it's only who they choose to prosecute, but that seems to be the problem with laws like this.
They aren't guilty of interference. Interference has a strict definition. A device operating in the ISM band by defition can't be interfering with other devices in the ISM band if that bandwidth is being used for communication.
ISM (Industry, Science, and Medical) is a free for all band. It is like a public good. Anyone can make a device that uses those frequencies.