The vent is used to take the temperature of the meat. The fact that it seals is great...that way, steam doesn't escape & when you're cooking with a slow cooker steam should not escape.
I own the 33967 Hamilton Beach Crock Pot too. It has a vent hole for taking meat's temp too, but it isn't sealed off. When I cook with it, I actually put a little toy magnet piece from one of my kid's old Magnadoodle's over the vent to cover it.
I should've complained during the warranty period about the Set n Forget shutting off but I didn't. The main problem with it is that it's very touchy when the power fluctuates & it turns itself off. I actually changed my review star rating after the Set n Forget turned off on me a few times. I noticed the newest Set and Forget has fixed that problem, but complaints are it cooks too hot.
I like this Crock Pot, but have to get used to not being able to program it as specifically as I could program the Set n Forget.
I'm sorry for the length of my comment. I really just wanted to explain the reason for the Crock Pot's sealed vent.