Actually, this rule (not to use speed mode with the autopilot off) was introduced in the OM-A way back in the 1990s, if memory serves me well. As the OM-A was binding for all operations, it became applicable for Airbus / Boeing / MD fleets (A306 / A310, A319-321, A330 / A340 AND B733-735, B742, B744, MD11).
Back to topic: I recently watched a YouTube-video. An ab initio pilot of an unknown airline had to do his “base check” (flying touch & go in the actual aircraft after completing the Type Rating). They flew the pattern with A/THR…
I am afraid that these pilots use manual thrust for the first time, when they have problems with the airspeed indicator (for example), which might not be the best time to train speed control / pitch & power and so on.