This is exactly right. Some cats like to be indoors only, some cats are ok indoors but would like to go out, and some cats need outdoor time like they need air to breathe. I once had a cat that I tried to keep in at night for the first seven years of his life. I let him out during the day but it wasn’t enough. I have a large screened porch that he could be out in at night, but even that wasn’t enough. He became increasingly stressed to the point that he was literally pissing blood. The vet said in his case it might be best to just let him out, so that’s what I did, and I worried about him every night until he died of old age and heart failure. His last years were happy, prowling and defending his territory (and yes, he was neutered, vaccinated, and wormed).
I hope Mr. O’Malley will recover and have many more years of happy prowling.