Joining the GS from above is not ideal... apart from any other reason, a modern clean airliner will not descend >3degreees without gear / speedbrake.
Ideally you do approach the GS from below, but descending iaw a CDA approach. The G/S requires say 700'/m descent, so if it works out well, you can be at idle, declerating from 200K to 180K at say 3-400'/m and intercept the G/S from below.
Of course, it doesn't always work out, and most will be well practiced in the "technique" to join the G/S from (slightly) above...
NoD