The article mentions one reason for small numbers predominating:

> The first is listicles. “3 ways to do X”, “5 things I wish I’d known”, “10 tools I actually use”. The listicle is practically the native unit of the link post, and its count is almost always small and round. Nobody writes “17 things I wish I’d known” unless they genuinely have 17 things, which is rare, whereas “5 things” is a decision made in a title editor.

But doesn't the title mangler specifically try to strip out numbers that look like they're part of listicle titles?

Yes, it does, and it's in the submission guidelines too:

> If the title contains a gratuitous number or number + adjective, we'd appreciate it if you'd crop it. E.g. translate "10 Ways To Do X" to "How To Do X," and "14 Amazing Ys" to "Ys." Exception: when the number is meaningful, e.g. "The 5 Platonic Solids."