A quick grep indicates at least the following modules use os.path but only import os:
bdb, binhex, cgitb, compileall, cProfile, doctest, filecmp, fileinput, fnmatch, ftplib, gettext, glob, imghdr, imp, inspect, linecache, mailbox, mimetypes, modulefinder, netrc, optparse, pdb, platform, profile, pstats, pyclbr, pydoc, shlex, site, sndhdr, ssl, subprocess, tabnanny, tarfile, trace, uuid, uu, webbrowser, zipfile.

So, it's a very common idiom.