I created a pull request with a small change to PG to enable easily disabling the equivalence message by passing "bypass_equivalence_test => 1" as part of the arguments to the cmp call.
See: https://github.com/openwebwork/pg/pull/497
See: https://github.com/openwebwork/pg/pull/497
Hopefully it will make its way into the develop branch and then into WW 2.16.
People with access to modify the main PG code on their server can just make the minor change in the PR to lib/Value/AnswerChecker.pm and try it out.