Seems like a lot of words to just ask why ArchiCAD does not utilize all cores?
There are only a few places in AC that are heavily multithreaded. The majority of the time, things are single threaded.
If you do not see lots of cores active during a rendering, it is due to the rendering settings. This topic (single vs multi core rendering settings) is discussed in various other topics.
One of the forum moderators
AC 26 USA and earlier • macOS Ventura 13.4, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB