Check this video , and the description of this video.
It could possibly help.
Thats a very good video and you obviously have great technical knowledge.
However, my take on this is slightly different. I think its all about the +5VSB (Voltage sure boot). This voltage has a rise time and amperage and a target 5V. Some PSU have 1.5 amp rating, some 2.0 amp, some only achieve 4.7V in actual usage.