That’s not what they’ll be doing. They usually offer a later flight and accommodation plays the ability to make another connection. They may be offering to transfer people to a Manchester flight if that’s what the passenger is requesting, but that would be up to the passenger concerned.
I think we’ve taken KLM for granted far too long now. For those thinking it’s a replaceable service maybe think again on that one, I can’t think of many other airports where interlining is as seamless and where the flight time to the hub is such that it feels like a short hop (particularly for HUY where it’s little as 20-30 minutes wheels up to touchdown!).
If passengers are transferring to MAN on occasion it means that people are booking LBA. The worse outcome would be people cancelling with KLM altogether and heading to LHR instead.