"By default, a ** in a pattern will follow 1 symbolic link if it is not the first item in the pattern, or none if it is the first item in the pattern, following the same behavior as Bash.". However, some dependent modules contain multiple nested symbolic links, and the option follow: true only operates for a single level of symlinks.

dir_foo

foo.txt

dir_bar

foo

dir_baz

bar

In this case
glob.sync('dir_baz/**', {follow:true, nodir:true}) returns foo instead of foo.txt.