I had a look at Tide’s source code over at github and it actually is implemented. Found the FrequencyRatios and this comment here:
// Sync
// Slight deviation from spec here.
// Instead of toggling sync by holding the range button, just enable it if the clock port is plugged in.
generator.set_sync(inputs[CLOCK_INPUT].active && !sheep);
Still couldn’t get it to work. The frequency knob seems to have absolutely no effect when clock is connected. A bug, perhaps?