Not a hoax. But a musical joke.
Not Mozart at its best. But Mozart nevertheless.
Good glissando practice.
Right hand to be played with only one finger, but not necessarily the same finger. Use 3rd finger for ascending glissandos and acciacaturas and use thumb for descending ones.
A better quality piece at the same level of difficulty, and with glissandos as well (if that is the attraction), is Clementi´s “Grand Waltz”
Best wishes,
Bernhard.