Daniel Bernstein (djb) is a well known and respected cryptography researcher so his claim carries a lot of weight. It's also worth noting that NIST didn't invent these post quantum encryption algorithm. Instead, they run a competition and select a winner. Djb's algorithm got a second place, so people were wondering if he's just being salty about it, though if NIST were really compromised, it's not hard to imagine they'll select a weaker algorithm as the winner instead. NIST has posted a response which might be worth a read.
Edit: added links to djb's original post