It turns out that (on windows) it only does that if it "detects shell meta chars"
From system:

If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing (this is "/bin/sh -c" on Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly to "execvp", which is more efficient.

Hence, nothing Windows-specific going on in this respect (except that the set of metacharacters differs between Windows and *nix).
-- 
Ronald Fischer <ynnor@mm.st>

In reply to Re^3: system and wildcard expansion? by rovf
in thread system and wildcard expansion? by BrowserUk

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