Were NSF Rules Designed to Protect Climate Fraud?

Michael Mann et al. claimed they were not required to share code according to rules allegedly made by the National Science Foundation (NSF).  These alleged rules seem unique.  For example, Nature contributors expect scientists who publish in peer-reviewed journals to not only share their code, but to do it quickly:

“Authors and journals should share data and code quickly when questions arise.”

This makes sense.  If the NSF issued a rule against mandatory code disclosure in time for Mann et al. to use it, it might have acted with the explicit purpose of protecting climate fraud.