I don't think you can really make any guesses based on how soon you hear or how the news is given to you. It's possible it's bad news. It's also possible it's really good and they don't want to leave him worrying when they could give him reassurance. And more likely is that it is unrelated to what the news is and is simply that they got a cancellation or the results came back sooner than expected.

Some examples. After I had thyroid cancer, I had a whole body scan to be sure there was no cancer left. I was told the doctor would phone with the results, then got a letter calling me in for an appointment. I freaked. Nobody had even suggested the possibility of any follow-up appointment so I was sure they'd found something. Nope. It was just 2021 and they decided to move to doing more in-person as the pandemic was easing. More recently, my mum underwent a number of tests and was told they'd make an appointment for her to come in for the results in about two weeks. Instead the doctor phoned. She missed the call and he didn't phone back again for two days. We all assumed it was probably just something like letting her know when the appointment would be or asking for her doctor's details because they'd hardly give news about cancer over the phone. In fact, I was secretly hoping it might be that no cancer was found, as it seemed possible he might not want to leave her waiting for good news. No, he phoned and told her it was bowel cancer with liver mets.

So there isn't really any pattern. A lot of it depends, I think, on their schedule too and sometimes whether results are available.