Why the Speedmaster reduced?

Omega had used the Lemania based automatic chronograph movements for some time before they introduced the piggyback Speedmaster reduced with the Eta 2892 on top of the Dubois Dépraz chronograph module. I have read this was done because the piggyback movement resulted in a smaller watch with (perhaps) the advantage of a lower price (than the Lemania-based Speedmaster automatic). Were they still using the Lemania based movements after the piggy back movement was introduced? Or was the piggy back movement just a stop-gap measure after the Lemania based movement, and before the introduction of the modern Valjoux based automatic chronograph?

Thanks for your reply. So it seems that perhaps for a period in time, the reduced might have been more readily available than the Lemania based movement. I suppose, from the sound of it, the Speedmaster reduced was a stop gap measure, sort of between the Lemania based movements, and the ETA 7750 based movement.