It doesn't matter who else they've got an agreement with. The other agreement is clearly suitable and a comfortable/profitable agreement for BA otherwise they wouldn't agree to it. I am absolutely certain of that.
My comment in regards to the loads was applicable to more so the 2 x daily flights that they have (cannot remember which days off the top of my head). But these flights are absolutely atrocious for passengers coming back into LBA.
You've got to go to MAN on these flights if you fly on anything between 08.00-15.30 otherwise you're gonna be stuck with a hefty connection in LHR which is far from ideal especially if you've been on a long haul or if you're a business passenger.
If they change to more suitable times, I agree, I could see the loads improving. But 62% still isn't great at the moment. This is the sort of route BA cityflyer would thrive on if they had ops from LHR - but this is never going to happen!