IO540-C4D5D
I think the problem has been that if you did (say) EGHP DCT EGLL (there's an improbable route) and set a flight level you would appear to get no filtering because you have no intermediate waypoints. It will assume you are at ground level at each end and, climbing en-route to your FL and then descending back to ground. So it will give you surface to 4000 ft above the FL for the whole route (hence your cranes).
If you instead went EGHP DCT SAM DCT OCK DCT EGLL you would get surface to FL plus 4000 ft on the climb and descent segments and FL +/- 4000 ft for the en-route segment.
Most people didn't do this and therefore assumed there was no height filtering.
Apologies for the silly designators but I'm not IR myself and don't have a chart to hand to come up with something more sensible.
Site speed is now much improved, however one thing that catches a lot of people out is that when they access a pdf (e.g. the AIP pages) nothing happens at all on the screen until the pdf has completed downloading so they think that it has locked up. Some of the pdf files are quite large and so may take some time. If you have the dial-up networking icon showing at the bottom right of the screen it will be flashing to indicate data trasfer is taking place which is useful as a check that it has not frozen.
Hope this is helpful
Mike