To make it clear for other readers https://en.wikipedia.org/wiki/Spread_spectrum

DSSS is choosing a frequency and will stay on that, FHSS is fast switching frequencies with a certain algorithm w/o you will notice it. But it says nothing about what signal is transmitted. It is like the old AM/FM. With FM Futaba had PPM and PCM receivers, although the FM part was the same, the transmitted signal wasn't.

The early 2.4ghz systems were based on older FM/AM transmitters so I can imagine the transmitted protocol by then was still PPM (servo pulse width), for sure today all is transmitted in a digital code where every brand has its own code.