Well, this is strange. I've just compared both versions (with and without code changes) on a different machine and these strike/blow parameters affect the sound output for both.
There do seem to be some subtle variations between the versions' responses to strike_timbre but this could just be my imagination.
Not sure what happened here, perhaps a sample-rate issue? In any case, I have closed the GitHub issue for now. I am still wondering if any other users have experienced this behavior.
@boonier I don't think there's any copyright issue as the Mutable Instruments source code is freely distributed... I'm not sure why the code you mentioned was commented out.
I made some changes to the code and built another version: