You're getting at the crux of the issue: it's very hard to distinguish legitimate DMCA takedown requests submitted by individuals from illegitimate ones, and occasionally, they're going to make mistakes. Anything that the author said in his emails could have just as easily been said by someone else who was trying to take down the content illegitimately.

At the end of the day, the best option is to use an attorney who knows the right procedures and would also run the risk of professional consequences if they submitted false claims.