Your Acros curves are consistent with the repeated testing I've done with that film in a variety of developers. Finally someone has confirmed my results!!!
It is something that differentiates it (in addition to reciprocity behaviour) significantly from TMX and Delta. I have consistently found contrast to be highest in the extreme highlight area of the curve. In ZS parlance, contrast typically increases slightly around Zone IX, and stays that way until it shoulders rather abruptly - as opposed to the far more gradual shouldering exhibited by nearly every other current general purpose medium or high speed film. As a result with normal development the highlights develop to much higher densities than its TMX and Delta counterparts.
I posted comparative curves for Acros, TMX and Delta a few years back to point this out and at the time I recall PE saying it was indeed an odd behaviour for a general purpose film (and would make it an interesting dupe film). My view is neither positive or negative. A curve like this can have its uses - particularly if one wants to use extreme contraction procedures without obliterating highlight detail.