Strong words. I'd like to understand your choice of words here.
> Categorizing yourself
Also known as knowing yourself, your strengths, and your weaknesses.
> purposefully stunt your growth
A wild assumption that talking to everyone will magically let you grow. Some people just prefer to focus on people that matter to them.
> ... reduce opportunity for growth
By choosing to compete in an area that is your weakness, you already limited your growth potential.
> ... wasteful use of life
So refusing to talk to everyone is a wasteful use of life. Again, I find it more wasteful to talk to anyone instead of people who matter to me. Unless it's fun, of course.
Learning about who you are helps you know your limits and boundaries, which means you can learn to do more within your comfort zone and how far you can stretch it, which means your comfort zone expands and you can do more. That's the kind of growth I think comes with categorising oneself.
An alternative is to do things which allow you to become more comfortable with a reasonable degree of personal risk. Which can include things like rock climbing which you do on your own.