I don't know if I want to answer until I find out when you became aware of the quote.
Given the lack of explicit mention against it elsewhere that I could find (unlike 2e and before, for example), I have already been buying your argument that the rules were silent on it being bad, and it feels likely it was intentionally left out. This would have made me come to that conclusion earlier. I'm not sure why there would be so much worry about players having knowledge here and sharing it, if it didn't impact what the characters did. It feels like if they had just meant "secrets" they would have said so.
I'm not convinced that if a wave of folks reading PDF copies of modules they were playing to get an advantage became a thing, that Crawford wouldn't say something about how they didn't mean to encourage something that extreme. (Now, maybe if they were paying for the extra module copies...) Similarly if there came a wave of folks who chose low INTs but kept a copy of the MM open on their phone. I guess someone could always ask him on Twitter.