Wonder why didn't they add GCM with ECDHE even though it is already in Win10 preview. I considered it strange that they added GCM with DHE in the first place when all the rest of the suites are ECDHE.
Does this update contain any additional security-related changes to functionality?
Yes. In addition to the changes that are listed in the Vulnerability Information section of this bulletin, this update includes changes to available TLS cipher suites. This update includes new TLS cipher suites that offer more robust encryption to protect customer information. These new cipher suites all operate in Galois/counter mode (GCM), and two of them offer perfect forward secrecy (PFS) by using DHE key exchange together with RSA authentication.
https://www.imperialviolet.org/2013/10/07/chacha20.html
Also, did they even add support for Curve25519? Or are they still forcing us all to trust the (almost certainly) tainted NIST curves?
Windows 7 and later do already support ECDHE + GCM, but only when combined with ECDSA. In practice, nobody can use ECDSA because old clients still need RSA certificates.
So we continue to wait for TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, which is clearly the cipher suite that everyone wants. Years later, still not available for Windows Server.