The GM names were/are Suburban Carryall (sometimes Carryall Suburban) with
3116 "lift gate" or "end gate"; or, 3106 "rear doors' The other names (barn doors and clam shell) are descriptive and cute, and are commonly used.
The rear (panel-style) doors perhaps allowed for easier loading and unloading (with the seats out?). The end gates were supposedly handy for carrying a full load of people (in seats) and their luggage on the end-gate.
