toolchain's CMAKE_CXX_STANDARD_LIBRARIES_INIT get overridden

Following advice, I am altering toolchain to include just _INIT vars, but I seem to hit a problem where what looks like Windows-MSVC platform file overrides CMAKE_CXX_STANDARD_LIBRARIES_INIT.

Do I do something wrong? I added print points at various positions and got following:

-- pre project()
-- CMAKE_CXX_STANDARD_LIBRARIES_INIT="" ; CMAKE_CXX_STANDARD_LIBRARIES=""

-- end of toolchain
-- CMAKE_CXX_STANDARD_LIBRARIES_INIT="vendor.lib" ; CMAKE_CXX_STANDARD_LIBRARIES=""

-- in 'CMAKE_USER_MAKE_RULES_OVERRIDE'
-- CMAKE_CXX_STANDARD_LIBRARIES_INIT="kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib" ; CMAKE_CXX_STANDARD_LIBRARIES=""

-- past project
-- CMAKE_CXX_STANDARD_LIBRARIES_INIT="kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib" ; CMAKE_CXX_STANDARD_LIBRARIES="kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib"

Do I do anything wrong? CMAKE_CXX_STANDARD_LIBRARIES_INIT is documented to be used by toolchains, but setting it there has no effect.