naw .. not impossible at all ...
.. the Fender Longhorn (boner) basses ran from '89-94 1/2, and then Fender returned to the conventional body shape for the '95 model year ... this transition also included adding the Posiflex rods to these early American Standards, and returning to the heel adjust truss rod ... that is where the slight confusion occurs, as Fender will often introduce changes mid year (they like July 1) and the change will generally be reflected as of the following model year ... hence, Posiflex rods mid of '94, advertised for '95 model year ...
... the American Deluxe basses were introduced in '95, and all four versions, the 4 string, fretless, 5 string and left handed all had 22 fret necks (ok, maybe not the fretless

), which featured the Posiflex graphite support rods ...
... bottom line, needs to be a heel adjust truss rod to get the Posiflex rods (but not all heel adjust will get the rods), seems like only American Fenders get them, as no MIM Fender or any Squier has ever had them ...