ATC provide hdgs & heights for the appropriate angle.
Aluminium
I maybe pedantic ATC provide headings as they can see where you are laterally but the CANNOT see where you are vertically.
They do advise that at X distance you should be passing through a particular altitude but they have no way in determining whether you are at 500 feet or 5000 feet if for instance your transponder had packed up.
In that sense you are controlling your descent profile and could just as easely take the distance/altitude points off a chart.
With a PAR they control and can see you in the vertical profile too so TECHNICALLY a PAR is not pilot interpreted while an SRA has a ?
I am being pedantic
Pace