'title' may refer to suffix or prefix, but i agree the descriptions should make the distinction. sounds like this title pack failed to meet your expectations
In the interface, they are separated into two tabs, 'titles' and 'suffixes'. So I would think a "title" pack that says that it adds "titles" would go in the title tab. Now, if the tab was labeled prefix/suffix, I'd see your point.
In game, bringing up the "choose your title" window opens up a window that has two tabs: titles and suffix. Very confusing indeed.
From reading the "titles" they offer I thought it was mostly obvious as the first letter in most of them was not upper case as in "the Useless" rather than "The Useless"
Of course they do, some of the titles you can get from these title packs are better than every single raid title in the game.... A couple title packs on the marketplace give you titles you can unlock by getting slayer achievements though (for example titles like the bouncer, or the lion tamer can be obtained via station cash OR slayer achievements).