Any of those could be the case. Guess it's understood that you will put a 2 or 3 on the end of the pip when you want to choose one or the other. And it goes further:

    /usr/local/bin/pip*
    /usr/local/bin/pip2*
    /usr/local/bin/pip2.7*
    /usr/local/bin/pip3*
    /usr/local/bin/pip3.5*
    /usr/local/bin/pip3.6*