CHC funding applies when a person requires one to one care.
Of course, it applies to other criteria too and these do include a likelihood of falling.
However, it is only one of many.
The CQC may state that and will make judgements in their reports but if you have 20 residents on a wing, with the majority of them being unable to do much, if anything, for themselves, needing to be returned to bed, taken to the toilet etc. and all being hoisted or pushed in wheelchairs, also fed and helped with drinks in their rooms, there are bound to be times that, with the best will in the world, the lounge might not be supervised.
As I said earlier, I can only speak about my husband's nursing home and your father's may be completely different with most of the residents in the lounge for most of the time. In which case, I would imagine it is easier for a carer to be available to supervise it which makes your grievance very valid.
If you are really unhappy, could you perhaps arrange for your father to be moved to a different home when he is discharged from hospital. It doesn't sound as though you, nor your father. like it very much.
Good luck with whatever you decide to do.