Is it true records are sealed to look better....

You should also know that there is such a thing as an LP resealing machine. Every Tower Records had one in it's back room; every returned LP was visually inspected, and a disc with no obvious defects (scratches, etc.) was cleaned of fingerprints (with Windex and a paper towel!), reinserted into it's sleeve and cover, and put into a sheet of plastic very similar to the factory one, and sealed. The LP was then put back into the store's racks, and resold to an unsuspecting customer. That an LP is sealed is no absolute guarantee that it is new. One thing that proves a sealed LP is actually factory-fresh is a descriptive sticker on the plastic wrap. Another thing to look for is a seal right on the edge of the cover; the record store resealing machine produced that seal, factory sealing machines didn't.

There is no such thing as "mold release agent." That is another urban myth.

I don't clean new Lp's either.  @elizabeth:  One of our local used record stores has a few sealed used Lp's.  I bit once, never again.

I think the term 'sealing' is being used in two different contexts here: shrink wrapping the jacket a/k/a a 'sealed record' and some sort of sealing agent put on the vinyl. I am unaware (not that I'm the last word on any of this) of a coating being put onto new vinyl to conceal pressing defects, but am certainly aware of used records being treated with all kinds of stuff to make them look clean. One of the many reasons cleaning used vinyl is essential-- to remove the residue of prior 'cleanings'-
As to concealing defects, there are some papers on file at the AES that discussed the value of carbon black being used not only as an anti-static agent, but concealing 'plate out' issues in pressing. 
My take on the mold release agent is that it is over-hyped as a problem. I do think a lot of brand new records are dirty, but that's because of the environment in which they are made and the handling of them before they are finally sleeved and jacketed. Some of the inner sleeves used don't help either. 
I do clean 'new' records whether or not they appear contaminated or have any paper flecks or other detritus from handling.