However, I await the final word on this topic with bated breath. Hopefully an ICAO guru will post the "final word".
I believe that
FWW has had lots of confirmation, already, that this level segment is in the design criteria (2 NM only if there is no turn between the IAF and IF). Also that this is intended to allow the aircraft to become stablised in preparation to intercept the GP from below.
I believe that FWW's question was more aimed at the way in which other pilots interpret this. Certainly, from the procedure design point of view, I don't care whether the pilot follows this practice or not. I am also aware that pilots who use FMS will have VNAV capability that allows them to intercept the GP from TOPD, if they want - and, if I understand the situation correctly, that is precisely what they want.
But I think FWW asked about the operational use (or necessity) of this "level" segment and whether or not other operators apply it.