Mullet bike with a little rear wheel was a funny idea on old Cannondale, Fat Chance or Ibis. it was a solution for small sizes and trial bike.1985 mullet bicycles. I don´t see many future on this idea ... This bicycle (the prototype) was design in 1982 (photo of the final product in 1985)and has 6" of travel. And if you wonder why they don´t have front suspension fork it is easy: In that era they haven´t invented yet.
PD it reminds me the RMX7 but you have to have very dirty glasses
View attachment 877250
But for the MCR Descender (and SE Hanebrink Shocker), the 24" rear wheel was necessary for keeping a standard wheelbase, due to the very very long stay ans suspension spacing. Same thing on first Cannondale, as John Olsen, one of the designer, told to me).
On other hand, the Unitrak suspension is still use on modern bikes…