[Analemma_]

I imagine it's nothing more complicated than "OpenSSL isn't the native crypto implementation on Windows, SChannel is". Microsoft's engineers are probably much more familiar with SChannel, and they don't want to have to test/validate two crypto systems in parallel. Besides, this should make OpenSSH better in the long run; it should be able to have any compatible crypto layer underneath.

[lukeh]

SChannel implements SSL/TLS as a security support provider (SSP), native crypto interfaces are WinCNG (current) or CryptoAPI (legacy). A port of OpenSSH that used the native crypto library would likely use WinCNG.

An OpenSSL-like wrapper around WinCNG can be found in Heimdal's libhcrypto.