I would think you'd need a directional movement to break the move.
Not positive on that, but I'd imagine IWT/CTM is similar to follow, in that once the movement has started you need something to break it.

The mapped key is not actually doing movement for as long as you are holding it down... its doing movement until the second step executes, which breaks the movement.
If you were to change the mapped key, from advance a step on press and release, to only release (default)... the first press would start the movement, which would continue until the second press.
At least, that's my understanding.

All good, if you have it working.