It's the same on Linux, depending on what manpages you have installed. free(1) is the binary. free(3) and free(3p) are the C function.

If you have more than one installed, `man` might decide to show the first one or it may interactively ask you to pick one, depending on whether it's been configured to be "posixly correct" or not.

procps may not be installed by default on BSDs or VMS or whatever other *nix flavour the person has. But then again quite a few of those systems also don't use bash as default shell(or at least didn't use to), so when the person above asks about "writing a bash script to just do" it's safe to make some assumptions about the target audience.