Your correspondent is correct. Mickey Naylor did indeed suffer a back-over wheelie in his Pro Fuel slingshot Medecine Man. This was I believe 1978.
Mickey had a new rear-engined car built by Dennis Priddle but never ran it.
Both Mickey and Rico's crashes were not strictly blowovers. Both were wheelies which went too far to be caught.
The difference is that a blowover is an aerodynamic phenomenon. In a "proper" blowover the car is travelling at sufficient speed for the front and back wings to be creating downforce (i.e. somewhere past 300 feet) and then something, usually a breakage of the front wing, unloads the downforce on the front wheels sending the front of the car upwards.
Hope that makes sense.
Yours in hair-splitting...Tog