My boyfriend overshares with others. how does this become a habit?

we both are aiming for the same college for our post graduation and i got the admission and he hasn't got in yet but he will. i was using his phone for a while and i got a notification from his friend and the text seemed strange so i opened the chat and i saw he told her about all the little updates about this college thing. whoever he talked to about the admission and the process in paragraphs. her replies were short but i don't find it necessary for him to give such little updates to someone he isn't close enough with. then i went through his dm and i saw 3-4 chats where he overshared like this. even guy friends. then i realised that this was a habit of his. i am the type of person who believes in not oversharing information about my life to others. i reassure him 10 times a day that he will get into that college then why does he need other people's opinions? what is the main reason behind this habit of his?
My boyfriend overshares with others. how does this become a habit?
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