The best example I can offer for this phenomenon is The Griffen's Limited Edition boxes. In the past five years, there have been 4 releases in glass tubes with rubber corks and sealant. All 4 of those years were terrible smokes; they tasted strongly of ammonia and acetic acid. About six months ago, I took several from each year out of the glass tubes for some conditioning. I have smoked one each of the oldest two and I've seen a remarkable difference in the flavor, however the acrid flavors are still there. I expect that will change with a little more time.
In contrast, the 5th year's vintage (actually the 2nd year linearly) was packaged in aluminum tubes with a cedar sleeve. That year was a spectacular smoke, and I'm disappointed I only had 4 of them to smoke in comparison (whereas I have 5+ boxes each at my disposal of the other years).
The point of aging tobacco is that the tobacco and oils blend, while gases (most specifically nitrogen and methane) are given off as part of the continued fermentation process. If you restrict the flow of air too much, you will trap those gases around the tobacco which I suspect will lend an acrid taste, because it alters the process environment.
That's my stab at it, I won't claim to be right. This is just what I've deduced with logical thinking.
Edit: To answer your original question, I don't think that altering the air around the tobacco will drastically change the aging. Normal air (which is, as I recall, about 21% oxygen?) seems to do the job just fine. I suspect the idea is simply to vacate the gasses given off, as I mentioned above.
