Interesting, I never heard about that system.
During my reply to another comment I stumbled upon another issue with how I thought pauses could work, so maybe instead of pause they distinguished dashes from dots by designating different knocking surfaces (e.g. wall for dash and wood(like bedframe or doorframe) for them?

The goal would be to produce different sounds so e.g. dot = tak and dash = tuk. That way only pauses would be for switching the surface and for intermission between phrases