No open review for any crypto functions in Windows is possible.
That's basically a fucking massive red flag.
The likelihood of them hiding backdoors in software that you don't know about simply because some company you worked at that had access to some of their actual source code didn't have all that source code is low.
Look at just chrome for example, which I've posted my rationale for here:
Not a chance in hell.
Have you attempted reversing code?
The NSAKEY conspiracy theory wasn't dismissed in the late '90s because people thought the NSA wouldn't backdoor Windows. The opposite is true; the NSA was so feared in the '90s that people didn't (and still don't) trust standards like DSA, for fear that the parameter generation algorithms they use were backdoored.
No, the reason nobody takes the NSAKEY conspiracy theory seriously is because if the NSA was going to backdoor Windows, they wouldn't do it with the ASCII string "NSAKEY".