Personally, I click on the launch threads because they're part of the current batch: a clear indication that they're part of the current batch (rather than just a generic "launch HN" announcement) is much more valuable to me than the reference to the type of business. The "Launch HN" title is used by non-YC people, meaning these threads come across as non-YC threads than YC threads.
I think on balance you're probably right that excluding a startup from the title is a problem though -- so yeah, in hindsight, I think you made the right choice.
I changed it to say "Launch YC" instead of "Launch HN" this time round, for reasons related to what you're saying. Doesn't seem to have landed though :)
Another thought I had was "Meet S21". Better? It would free up a char! "Meet YC S21" is too long.
"YC S21" would be the shortest. That is, something like "YC S21: Foo, Bar, Baz" with a word or phrase for each startup. But I'm not sure if that would convey that it's a launch thread.
Another possibility: "YC Launch" instead of "Launch YC".
Our original idea was "Meet the Batch" but that's way too long.
I think on balance you're probably right that excluding a startup from the title is a problem though -- so yeah, in hindsight, I think you made the right choice.