I have noticed that a lot of devs just never playtest WIPs at all. They think it's entirely the job of the people who play it to discover and report even the most obvious and game-breaking of bugs. But this is even worse, because we are finding bugs and the dev is just saying "nah there aren't any." Not "Sorry, I haven't been able to reproduce that so I'm not sure how to fix it." but just "No, you're wrong, it's not bugged."