Hi, my company ask for permission to access records but in practice do not unless an issue arises with long term illness. For example we had a colleague with a degenerative disease, periods of sickness became more frequent and extended, eventually work performance suffered, at this point we asked for him to be assessed by a doctor of our choice. Even though we did in theory have access to his records we did not ever do so.
So giving permission does not automatically mean they will rummage around.