We get in the habit of accepting ATC descents below published MORA, route, or even arrival altitudes because ATC has min vectoring altitudes which are not published for our reference.
Also ARRIVAL crossing restrictions are usually there for airspace management reasons, ex separate departures from arrivals. ATC can waive those if there's no traffic conflicts and they often do.
But APPROACH restrictions are often there for terrain clearance purposes, especially closer in. If you're actually established on the approach course, you should question any clearance to descend below published altitudes.
If given at or above, might as well just comply with published, especially in mountains on a non-precision approach
As always, maintain terrain awareness at all times.