Why they say "DO NOT USE BEACON GENERATED VALUES AS SECRET CRYPTOGRAPHIC KEYS"?
ASCII:
entropy sources -> entropy pool -> CSPRNG -> ...Given that you'd probably want to avoid using for any crypto use (not just secret parameters) unless you can be sure that using this randomness for a public parameter doesn't break the cryptosystem (or USG isn't in your threat model). Given that few of us are experts in cryptology it would seem like the safe thing to do is to avoid for crypto use at all.