what's the point of this?

"I block all online ads" is a less useful title than "How I block all online ads", and pointing out when the title mangler has made the title worse serves as a request to moderators to fix it if they agree. Which they did here, I believe for a net win.

I meant what's the point of truncating the title like this

An anti-clickbait measure, IIRC. I can’t, off the top of my head, think of an example this prevents, though.

an early anti-clickbait feature that dropped “why” and “how”; you can manually edit after submission to append the ‘how’ or ‘why’ back onto the article.