Usually and as per the documentation, input globs use forward slashes and the result paths use the native file separator.
But here are examples of globs on Windows which return forward slashes (a bug):
glob('C:/') //=> ['C:/']
glob('C:/Users') //=> ['C:/Users']
glob('/') //=> ['/']
glob('/Users') //=> ['/Users']
glob('./././') //=> ['./././']
Basically any glob which has no operators inside such as * or {} just returns the string as-is without any post-processing, even when it contains the wrong path separator. Note that the path must exist for it to not return zero results.
The result I expect is the same path I entered (not resolved or normalized or anything) just with the native path separator.