I think the 18 is the 2330-0600 quota. INBOUNDS and OUTBOUNDS!
As for appyling "a reasonable amount of power" it stops them falling out of the sky around Richmond/Twickenham.
A lot of posh houses/MP's there so power over Waterloo acceptable.
Seriously, they apply no more thrust there than anyway else on final - and at least they are higher than those closer to the field.
As for the media; Don't believe all you hear or read or see.