PCGS Holders are NOT Sealed at the Top!

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Has anyone else noticed that PCGS holders are not sealed at the top?! This came as a bit of a revelation to me when I examined my PCGS-graded notes more closely (see scan below). Although an attractive piece of high-quality green paper is stuck around the top of the unsealed holder an air gap remains on the left and right sides of the green paper at the top. Thus, the note inside the holder is in direct contact with the environment outside the holder. This could potentially be dangerous if the holder was exposed to water as the water might imbibe into the holder via the well-known phenomenon of capillary action. By way of example, I once carelessly spilled a glass of port on some holders containing notes and the notes became stained red in a matter of seconds!

http://www.cdnpapermoney.com/forum/index.php?topic=4248.msg27149#msg27149

Incidentally, BCS and PMG holders are sealed at the top so the notes inside are fully protected from the outside environment.

http://www.cdnpapermoney.com/forum/index.php?topic=9404.0

{http://img.villagephotos.com/p/2008-1/1293040/PCGS2.jpg}

Does PCGS actually claim that their holders are airtight? 

Does PCGS actually claim that their holders are airtight? 

I don't think PCGS makes any explicit claims regarding airtightness but it seems to me that most collectors assume that any TPG-graded note will be protected from the outside environment, at least that's what I used to assume. PCGS presumably has good reasons for leaving an air gap at the top of its holders.

CCCS and CCGS holders have two small perforations (look like half a paper punch hole) at the side edges which I understand is to allow the note to breathe.  I'm not sure of the importance of this but the possibility of spilled water coffee or wine seeping into these holders also exists.

From what I was told the lack of air might cause the note to disintegate over time, I was also told not to put a note between two pieces of glass for the same reason.

I have done some research into this matter, seeing as how my Banknote Certification Service does not perforate their holders and hence, does not let them 'breath'.  I have contacted some paper conservators and their answers are consistent - due to the high quality paper used in the making of paper money as well as the type of inert plastic used, air tight long term storage should not be an issue for generations to come.

Now I don't know much about the chemistry behind this; I'm a numismatist, not a chemist.  However, I'm willing to take the word of someone who does this for a living.  Believe me, I looked into this with serious trepidation.  The last thing I want is an angry mob after me because my holder has destroyed their prize pieces.