Just noticed, at least on mobile web for mastodon 4.4, pinned posts beyond the first are hidden behind a tiny left/right widget at the top right. This makes having multiple pinned posts pointless since let's face it, nobody is gonna see that tiny widget let alone feel compelled to click on it. So this effectively makes mastodon less unique and more like every other social media platform where you only get 1 pinned post
Sure, you're technically allowed more, but nobody will ever see them