I saw no APS in 3D! These were much before APS.

I have seen several "talkiing" photo methods. None related to APS went beyond the early talking phase of R&D. The others existed as you say and were simpler.

As for the APS size, you must remember that at that time EK was at the sharp edge of sensor production even though they lost out. The format chosen to match sensor and film sizes was made for economy as sensors were quite expensive. The name APS and the sensor size and film dimensions were planned on by all involved.

There was lag and lead in both the film projects and the sensor projects at EK, but the first sensors were much smaller and fit in the window of an EPROM. I have held some of those first samples at EK and have held the first digital camera.