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

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. 

Let's be very clear about this "mold release agent" thing and put it to bed once and for all. The hot vinyl biscuit gets deposited between the two preheated stampers and the biscuit is then pressed. The stampers are cooled via water jackets, separated and the record is released from the press. There is no added anything to the process. There is no "PAM" that is sprayed onto the stampers or treated to the prestamped biscuit. It is simply the vinyl substrate on the record surface, nothing else.

I'll say it is a LOT easier to see defects in the vinyl if it is BLACK. Clear or transparent vinyl is near impossible to see small imperfections in the grooves. (at least in my experience)

New records don’t need to be cleaned. There’s no mould release nothing, never has been, never will. Just nonsense from the misinformed. Ultra sonic cleaners are snake oil.