The only "add-on" normal kickstarter backers have is the "You rock" message in the main menu. Apart from that the game is absolutely identical to the release version + DLC.
Only high backers ($150 and more) have special items or perks like a personal pet. But that's just how kickstarter works. These people (like me) "invested" a lot of money early in development and in return they get a sign of appreciation from the devs. And only very few people have backed on that level compared to the tousands and thousands of people who backed at a "normal" level or just bought the game during Early Access or after release...
I think you're just misinformed and exaggerate based on that misinformation.. And tbh the DLC ingame items are barely noticable in the game anyway.
