Here's what's going on. The only way to vacuum pack coffee is to roast, then let it sit in open air for 24 to 48 hours so that the carbon dioxide can let off gas. That is what "vacuum sealed" coffee is – it's stale.
What we do is a little bit different. We take warm coffee from the roaster and put it directly in the bag, then we flush it with nitrogen and seal it, with a one-way valve (this is the clear square piece on the back of the bag, pictured below)
Over time, the coffee will release carbon dioxide and push some of the nitrogen out through the valve. If you feel a bag full of "air" is not supposed to be oxygen, and will help freshness.
If you get a bag that is "vacuum sealed" from Bulletproof, what happened is that the nitrogen and carbon dioxide have been pressed out of the bag, often because of air travel, and the one-way valve was strong enough on the descent to maintain the vacuum.
It is well known in the coffee industry that some small percentage of valves do not hold the pressure, so if this happens and your coffee does not taste fresh, you can send it back and we will replace it. Dave (our CEO) can even attest to never having received a bag that had this problem, resulting in stale coffee, but there have been some bags with valves that perform better than others.