Veracity of albums for sale being "sealed"?

always possible, but real sealed originals just get more rare by the day. clean unworn covers are priceless for many titles.

The 'sealed' IMO means nothing without the original buyer's authentication. So resellers with sealed... it's all going to be trust.
As an aside, one kind of LP, Columbia, had a unusual sealed inner plastic for a few years, and THAT one is pretty much a guarantee of 'sealed' (I have one, still sealed).
For myself, I will pay ZERO dollars more for a sealed LP.. Plenty of unsealed LPs have never been played anyway.
All the hype about sealed is for it's 'collectable' status, and not the music.

most all lps were sealed using shrinkwrap. Shrinkwrap, surprise, shrinks over time and the results were often warped records. Leaving the shrink wrap on an opened record was generally considered a bad practice. I'd be suspicious of any record that has been sealed in shrinkwrap for many years. The clear benefit of course is that the cover is protected and may be in good shape as a result.