Interesting discussion. Had the case recently that i was cleared for the ILS out of 6000ft instead of 4000ft and of course reduced speed during G/S intercept to achieve the initial approach configuration. As we were quite busy we forgot to tell ATC about the speed reduction and got a pretty strict sermon shortly afterwards. However, remaining at 220kts while on the G/S is simply impossible, the aircraft would accelerate if not configured and that would lead to a go around very shortly afterwards. To configure we need to reduce speed, so it is pretty much basic aircraft performance 101 that G/S intercept will lead to a speed reduction. By the way, no further speed control was given with the approach clearance, last speed given before was 220kts in a 738 and the usual 10 to 15 kts tailwind one encounters in ZRH at that altitude.