This is what the various gamma settings result in (from -10 EV to 6.5 EV, with Pascal’s recommended contrast of 2.8 and toe/shoulder power 1.55), if the default gamma, 2.2, is applied to the linearised result (note that auto-gamma internally scales the user-specified contrast to deliver the same contrast around the pivot):
dotted line: gamma = 1 (never really produced by the auto-gamma)
red line: gamma = 2
green line: default gamma 2.2, for reference
black line: gamma = 5
Except for the low-gamma line, they do run rather close together, with the rather extreme gamma = 5 delivering somewhat deeper shadows and brighter highlights, indeed.