Agreed. But the usual methodology is to collect everything after it's been printed. Much less common is to do a "brand new book collection" where nothing has been printed before. This is usually lit stuff. It's not uncommon to offer a new story or two in a collection of otherwise reprinted stuff as a way to make sure there's something in it new for everyone and make everyone buy the book but I really dislike this as it just means that, if you haven't followed closely, it makes no difference and if you have followed closely then you indeed have to spend a lot of money on almost nothing new or miss stuff - and it's really always the latter and that doesn't do the author any good either. (Like having a "bonus track" on an album re-release or "Japan-only track" or something in music - just annoying.)
Best to just collect only things you've published elsewhere.
(Of course, all that said, it's virtually impossible to publish novellas in magazines or online these days, so I could see including those in a collection that's otherwise reprints.)
