It is a presumption, but based on destinations, i.e. caribbean, cancun, maldives and soon to be mauritius. Not quite Baltimore, Houston etc. And I suggest that on leisure the club experience is something to be savoured more than if on business. At least thats what I would expect if I had the cash to pay for a club seat to go on holiday. Even BA note that LGW is to be a premium leisure hub according to the latest 'up'.
On all my flights someone from econony is not two assists in club when their service is over. Cannot comment on all BA long haul flights because I cannot physically be there to see. Can you?