Tenacity inherited various experimental features from Audacity, some enabled and some not enabled. MIDI was one of them.
We have a bit of experimental MIDI stuff lying around in our codebase, including a MIDI (i.e., note) stretch feature that's documented to be broken and buggy). Just recently, @gperson (that's me :D) got the feature to compile again. It didn't look like it worked, but it was tested on Linux when it was documented NOT to work.
The mysteries await 🤔...