Yes.

Not everyone likes squashed/rebase workflows and it's frustrating to have to police people. A lot of groups use a workflow where all commits to branches of global interest are strictly pull requests.

For those who are in this situation, consider that what you can do is test _only_ merge commits - that is, put something like this into a script:

    if git log -1 --pretty=%B | grep -q 'Merge pull request'; then
       # tests here
       exec the_actual_test.sh
    else
       exit 125
    fi

... then "git bisect run script.sh". This skips the intermediates and only tests merge waypoints.

Edit: someone below notes --first-parent option, which basically accomplishes the same thing.