Unfortunately due to issues with the release process we have inconsistent source code between the 3.96.0 tag in the NSS repo and the code that is on the FTP. The code for 3.96.0 available on the FTP contains some changes planned for the next release (namely DTLS 1.3).
As we cannot change what has been published on the FTP easily, and to avoid further confusion, we published a dot release...
As part of our roadmap to improve release automation, we will design things to be resilient against this divergence in the future.
NSS 3.96.1 is available consistently in the FTP, the repo and Firefox as expected.