Like mentioned previously, "friendly" might be mistaken for the animals that just don't want to be caged and would prefer to be anywhere but the cage. Just because they want out, doesn't mean they want to be with a person. There are exceptions of course.
The general guidance of "don't hold them much" is just that, something to guide you. Each animal is different, but let's face it, not holding it isn't going to kill it. Better safe than sorry. Plus, the subtle signs of stress can be incredibly difficult for even experienced keepers to notice, let alone new keepers. I would much rather let them be if they want to, than force them to come out when they don't have to. Stress can very well cause issues that lead to their demise.
I had a male who literally would crawl across the room from his free range to where I was sitting and doing work just to hang out. He even liked some of my friends and would hop on for a quick look around when they walked by. I would consider him sociable with humans because he actively sought humans out even when we weren't near by. I never actively handled him and he picked it up on his own. I also have a male veiled who went crazy the entire few days that I tried to free range him. He cannot stand human interaction that is not feeding time. He likes his routine that involves almost no handling and that's the way he is. I am happy to let him be because he is most comfortable that way.
