It wasn't a DMCA takedown notice. It was a DMCA section 1201 notice. Section 1201, which criminalizes circumvention of access controls, has nothing to do with copyright.

John Deere uses it to go after sellers of unauthorized replacement parts for their tractors.

Non-compliance is a felony carrying a 5 year / $500k punishment. Unlike takedown notices, there's no counter-notice opportunity for the receiving party. So if the receiving party believed the notice isn't valid, they'll need to argue that as a criminal defendant in criminal court.