Yes! This is me too! It's such a relief to see your comment, it's very isolating to experience 'social anxiety' but in a different way.
I've experienced both types of social anxiety that you mentioned and I worked really hard to overcome the 'classic' symptoms. I can now do all the things that used to inhibit me. Sometimes I feel uncomfortable and if I haven't done it for a while it feels worse, but I can also be more fearless than many peers.
But the crippling anxiety has been exactly as you describe it - the social anxiety that grows as time passes and the more that I fight it and push myself the worse it becomes.
I've been too afraid to finish many things that I've started and it's destroying my life to be honest.
Working on it alone I've come to the conclusion that it's related to an inner sense of shame. It's like I'm afraid that as people get to know me they get closer to finding out what a terrible human being I am. So it's really intimacy that is scary.
I've been in situations where I've confessed how anxious I felt and was embraced and accepted by people and I only felt worse after that. I felt like an imposter and couldn't relax until it got to the point that I had to quit due to panic attacks and depression.
Studies, jobs, sports, I have to quit when I feel like everyone can see the real me and I can't stand being in the room anymore. One-on-one relationships are easier but I've quit plenty of those too.