The "Continuous Descent Approach" technique, in use at LHR and preferred at many other noise-sensitive airports, meant that one regularly intercepted the GS from above.
The ideal was to roll out onto the LOC and GS simultaneously, but inevitably there were times when one intercepted from slightly below or slightly above. The idea was to minimise level flight with its associated engine power and noise. As mentioned, no big deal if one monitored DME, Altitude and VS.