[masklinn]

That's pretty common IME though the ones I've driven didn't make decisions based on that.

Last few cars I've rented had a speed limit sign generally matching the speed limit on the dash, and on the one I rented this christmas passing a speed limit sign (or an other sign triggering a speed limit change) while on limiter or cruise control would flash a message suggesting pressing a button twice to change the configured speed to that (rather than manually adjust using the +/- buttons).

They were mediums (C-segment) and compact MPV not large or luxury, which I expect is why the sign reading was mostly to purely indicative.