If ur a person that has sex on a regular basis, you prob dont have much boundary issues, whereas insecure, shy, nice guy virgin has boundary issues, confidence problems, awkwardness, unsure of their body language
Not being able to touch a girl who clearly is comfortable being next to you is NOT in the scope of regular shyness. That's not being mister totally at ease. If you can't handle that, you have some serious issues man. And for that I am sorry.