Hi crankcase. IMHO I think the main reason they're looking for good A level results is because they want to minimise the risk of you flunking the ATPLs.
As you may well know, these schemes are run on a cut-throat budget where having to do resits is frowned upon due to the extra cost and the extra time taken.
By selecting people who have a greater chance of passing the ATPLs first time they reduce the risk.
You're right about the flying part but let's face it, if you can drive a car you can learn to fly a plane in time, to some extent.
Besides, my ATPL studies tell me that 95% of the time the damn things on Autopilot anyway! Who needs flying skills?!