I don't think it's accurate that there is "no way" to "prevent your mac from using the headphone's microphone." There are several workarounds like creating an Aggregate Audio Device in Audio MIDI Setup [0] or disabling HFP [1]. I wish you success with your paid utility though.
[0] https://www.reddit.com/r/MacOS/comments/n6trw3/comment/gx98u...
[1] https://discussions.apple.com/thread/7495115?sortBy=best