Chain wax has been somewhat common in the road/criterium/track/MTB/DH/XC/trail/enduro/…. Circles I’ve been in for the last >40 years. I think it is a way more common practice in dry dusty regions.I would be interested in seeing how it works. I don't see wax lube in the pedal bike world much. I used wax all the time in off-road moto but more for the o-ring chain. Not sure how well it would work on the MTB world.
It extends the life of your drivetrain exponentially! I have a buddy with around 10k miles on his Durace drivetrain, yes even the cassette and chain.