aviexp, I'm not an approach controller but I'd say you still need to report the level maintaining. If nothing else it confirms that your transponder is correct. Aircraft do occasionally "prop" at intermediate levels without saying anything - adjusting profile I guess.
Technically approach doesn't know you're maintaining F200 unless you tell them because they have no knowledge of what your previously assigned level was.
I suspect the example quoted when calling approach is really only catering for aircraft already on descent.