Dude I'm far from an extrovert. I just don't understand being that shy around someone who is your friend or very least an acquaintance
My point exactly. You wouldn't get it because AT THE VERY LEAST, you are not down in the introvert scale. I guess introvert isn't really the name for this phenomenon? I'm sure there was a specific name for this shit, but I do not remember.
Anyway, for them, EVERYTHING regarding opening up to someone or just plain being honest with them is hard. That's just how they feel. As they grow up and interact with people, some may grow past being embarrassed, some may still be embarrassed. It depends on their own effort and the support of the people around them.
If you don't get it, cool. Good for you for not having to experience this awful aspect of life where your shitty actions and words would hurt the people you love just because your ass couldn't be honest with yourself. I already went past that aspect of myself, but I still remember how hard it was for me to open up and be honest with people (sometimes I went back to my old ways when I'm stressed, but I try my best not to).
That kinda stuff is also partially why the tsundere trope exists. The trope just exaggerate the reaction for comedic effect.