The extrapolated volition of a cultural group might, given certain assumptions, resolve to a single set of values. If that were the case, you could express changes in expressed volition in that group over time as either progress toward or regression from that EV, and for various reasons I'd expect them to usually favor the "progress" option. I suspect that's what cousin_it is getting at.

I'm not convinced that we gain anything by expressing that in simple terms of progress, though. The expressed volition of modern Western society is probably closer to the CEV of humanity than the cultural norms of 500 BC were, but cultural progression along the metric described above hasn't been monotonic and isn't driven by reference to CEV; it's the result of a stupendous hodgepodge of philosophical speculation, scale effects, technological changes, and random Brownian motion. That might resolve to something resembling capital-P progress, especially since the Enlightenment, but it's not predictively equivalent to what people usually mean by the term.

And it certainly can't be expected to apply over all cultural traditions. The check on CEV described in the OP, however, should.