Yes, I think that's the important distinction. It's all about whether or not you're cooperating with others to secure the goal, or working by yourself. In all the sports I've described above - you are not cooperating with others to achieve the same goal - except for the more nebulous "have fun" goal :)

The fact that others can be involved while you practice is a secondary matter - that only concerns you if you literally want to be by yourself... which as you say - is not likely to be the case.