Whilst I agree, two quiet people getting together as friends may not always be the best option. I can see it's a kind of "safe" place, a kind of comfort blanket, to be friends with someone just like you, but I'm not sure it's the right thing for the longer term.
My son ended up very friendly with another student at Uni, who was just the same as him, very quiet, shy, introverted, he had diagnosed ADHD. Both were doing the same Maths degree and they ended up flat sharing in the third year. But it was to the detriment of making other friends, as they were "comfortable" together, living together, same lectures, same tutorials, same seminars, same exam, travelling together on the same buses, studying together in the library, etc. It basically meant neither of them "needed" to look elsewhere, so they didn't socialise with anyone else, only went to the same clubs together, etc. It actually caused my son to be more shy, quiet and reclusive! As I say, a kind of comfort blanket. He ended up actually resenting his friend by the end of Uni as he felt he'd missed out on so much, and felt he'd actually been dragged down by his friend.
I think that's what caused him to have a full "reset" when he started his first graduate job and threw himself into everything on offer at his new employer and with his new workmates. He must now have a couple of dozen friends who he does different things with, he goes to pub quizzes with some, five a side football with others, going to watch footie matches with others, cinema with a different group, plus all the usual works socials such as team lunches, team drinks, etc. The change in him since his reset upon starting work has been amazing - he's completely different, far more social and outgoing, far more confident etc.
Sadly he barely has any contact with his Uni friend anymore - they kept up facetiming and online chat at first, but DS has basically lost interest as his friend didn't get a job so was stuck at home, still playing computer games in his bedroom, never going out, and they basically ran out of things to talk about when they didn't have the common interest of their Uni course.