This kind of thing is normally used for quick light pickling, maybe a day or two in rice vinegar. I tried it out as an alternative to ordering mason jars with weights and nipple tops, which would end up being kind of painfully expensive to get to Japan.
It wasn't obvious to me when I ordered it, but the lid just sits on the container and has a couple of not-quite-latches that hold it down only if there's enough upward pressure from the spring pushing against whatever is in there. And it's made not to seal. So if my idealistic assessment is right, it should let a CO2 blanket form and easily push the rest of the air out.
I guess we'll see how it goes. My pepper plants should start producing within a couple of months, so hopefully this ends up working well.