Do you think it is very unlikely for two very introverted people to date? I always see either two equally loud people or one load and one quiet person dating. People know the quiet, cute wallflower dating some alpha male, but the load, aggressive Karens dating beta males are just as common. And then there are the couples where both are talking over each other non stop.
But I can't think of any introverted couples in my family or my limited social cycle.
A relationship where no one gets the other one out of their shell sounds like it's doomed to fail or won't happen in the first place.