I believe it's likely the post is legit. I've toured Print shops and I've been trained at working a press. I've a good idea of what can go wrong and personally find it amazing when anything actually goes right.
However you do have a hard case to prove after 6 months.
If I were WotC I'd want to see the book in person to be sure there was no glue on the inside, and the moment I found the razor blade marks I'd be very unlikely to validate your claims.
That said; my books have held up very well. Which is the case for me with all my RPG book from various games despite all the claims I always see on the net.
I've only ever had one book fall apart. 1st printing of 3E GURPS. The glue on the 'perfect bind' hardened and cracked off. But the book was also not well treated. It was a buy in the days when I'd learned to handle books right after getting into 'Comics speculation' but before I'd started a full 'hands off' policy on my books with my fellow gamers.
I'd also been a fool and followed SJG's own advice and 'flattened the book down' to make it easier to read.
Something I never do now. I've caught people grabbing my books and trying to do it and it's a very good way to really tick me off.
I watch people at the table who claim they treat books well... and I've only seen one, maybe two people in the last 15 or so years since I started taking care that actually met my standards. Most of them; I know full well why their books fall apart but I refrain from saying anything to save their egos.