From a pilots perspective I wouldn't descend below a final cleared level until the glideslope was intercepted. Therefore descending below that level before intercepting the glideslope should never arise - although it would appear that it has.
Secondly it is also a matter of setting up the automatics. In the Airbus you just push the Approach button on a localizer intercept heading and it will intercept the localizer and the glideslope, in that order. In the 737 you press VOR/LOC first and the Approach button only after localizer capture. In either aircraft a glideslope intercept from above can be a hazardous procedure. The autopilot either intercepts a lower altitude, therefore making your approach even steeper, or if you have set a higher altitude you are now pointing at the ground with nothing but glideslope capture or the GPWS to save you from hitting it.
Therefore to be cleared for an ILS (including the glideslope) is by far the safer procedure.
[This message has been edited by Flap 5 (edited 19 May 2000).]