The official Bitcoin Windows binary isn't built with VC, but it does use the Microsoft Visual C++ Runtime (msvcrt.dll).
What do you know. You're right! I just tested it with InspectExe and indeed msvcrt.dll is in the list of dependencies.
That is the C RTL not the C++ RTL, and indeed mingwin uses the msvcrt dll to avoid the need for gpled code at runtime.
Yes, it is C standard library specifically, but it is considered a Microsoft Visual C++ Runtime Library (there is no Microsoft Visual C) and I'm guessing that is what the error message is referring to.