If there is genuinely a problem with a shortage of tables, the common sense thing to do here would surely be to reserve a certain number of tables for F passengers and then allow CCR users access once it is confirmed whether there will be space either because the F load is light, includes a lot of CCR holders/double counting or because some F passengers have decline to dine (IAD is where I've used pre-flight dining most and you are typically asked on entry 'will you be dining before the flight' or similar). I suspect that is not the real issue here, however!
In particular, I'd like to point out I've encountered the issue of there being no free booths at the CCR at LHR more than once, but never had the same issue at an outstation!