True FHSS isn't -- but our RC systems (despite the claims) aren't "true" FHSS.
With a true FHSS system, the signal is transmitted on a very narrow frequency that is constantly changing (hopping). This means that any individual frequency is as easily blocked as our old 72MHz gear used to be.
DSSS systems work by combining the data with what's called a "spreading code" which means that instead of taking up just a very narrow space (like our old 72MHz systems), it is spread across a wider range of frequencies. It is therefore harder for interference to knock out a DSSS signal because much of the "good" signal will lay outside the area of interference.
Now, what we've done with our "FHSS" RC systems is combine DSSS and FHSS to get a hybrid that should really be called "constantly agile DSSS".
These RC systems use a spreading code to "spread" the signal so wide (usually 1-5MHz) that it becomes very resistant to interference. Then, to increase the interference resistance even more, the DSSS signal is constantly moved up and down the band (by hopping).
So, while a "true" FHSS system may in some cases be worse than DSSS at handling interference, our hybrid systems represent the best of both worlds.
The original poster clearly didn't understand exactly how our so-called FHSS RC systems actually work.
RCModelReviews.com, just the facts.