A clearance for the approach is an instruction to follow the vertical profile of the approach without further ATC instruction. Descent to subsequent levels is implicit. Why should that implicit vertical profile not start at the IAF with the charted altitude there?
Another example: I'm being vectored for an ILS at 3000 ft, a level above the charted FAP altitude of 2400 ft. The controller says "closing the localiser from the left, cleared ILS approach runway xx". I intercept the localiser and the glideslope comes in 2 miles before the FAP. May I descend? By your reasoning, I'm not on a published segment of the approach yet, so don't I have to wait until I reach the FAP before descending?
First, I tried to find the cited approach on-line, but was unable, so I don't know what it looks like.
For many/most non-precision approaches, the IAF altitude is a "soft" (recommended) or an "at or above" altitude. If your cleared altitude is reasonable, even if above the minimum or recommended, you do not have any reason to descend below your cleared altitude. You may, however, need to configure the aircraft to obtain a steeper-than-normal descent profile from the IAF to the FAF. If it is a hard altitude, ATC has the responsibility to get you there.
In your example, you are being vectored to the localizer, which is a different situation. The FAF for an ILS is not always a fixed point, but is defined by Glideslope intercept after established on the localizer. if you intercept the localizer outside the nominal FAF depicted on the approach plate, you can descend on the Glideslope as long as you are within the service volume of the ILS. For example, look at the ILS to 06L at KLAX. Though the nominal FAF is at ALISN ([minimum] 1800' at 6.7 DME), there is a note that explicitly allows intercept of the GS as far out as NATHN ([soft] 3700' at 12.7 DME). ATC will often vector to intercept the localizer at some intermediate point/altitude, and you can intercept the GS if cleared for the approach.