A bunch of my CDs were sealed too. They often don't even bother mentioning it.
And, like @Ken Dryden said above, their grading is very trustworthy. What they call VG+ typically looks like NM to me. And this true of both their CDs and LPs.
Because their grading is so "conservative," I often buy VG graded LPs from them. (With other online retailers, I typically won't go below VG+.) After a couple spins on the vacuum machine, their VG-graded LPs typically play very, very well. Maybe not PERFECTLY. But much better than what you usually get with a VG-rated platter.