Proscriptive describes certain musical policies, it does make sense, for example some traditional music clubs[ not the singers club]had proscriptive musical policies, those policies forbade anything but unaccompanied singing, that description is crystal clear, the singers club had a different proscriptive musical policy.
Neither does it follow that clubs like les cousins who had a broader and less proscriptive policy had any lower quality of booked performer, they too had a high standard.
"If being "proscriptive" means doing what you say you do"
That is not the definition of Proscriptive.