i'm sorry, I think I made a goof
Port Q is not on Throttle Body as I remembered it hehe, it is actually the passenger side of EGR modulator named as Port Q and this port is in fact connected directly to VSV for EGR, you are correct.
what you said is correct, ECU cuts off EGR flow under conditions you mentioned.
I had a thread where some of those troubleshooting issues were covered, JohnGD was supplying me with info while I was trying to figure out some idle issues and intermittent power loss problems upon acceleration. It was a very long thread (20 pages?) but somewhere in it it was all discussed. will link it in a sec.
[SOLVED] 2000 camry gen4 5sfe short and long term fuel trims
I ended up replacing all 3 EGR parts, modulator just in case as it has a filter and backpressure port has a diaphragm which is impossible to clean and can get sticky/clogged.
I destroyed EGR valve in process of cleaning (bolt broke off holding it down to exhaust pipe), was sticky anyways, got new one.
I replaced VSV for EGR as testing it on car was showing some intermittent problems with energizing, but when I tested it off car (jumpered to battery) it worked fine, so I sold old one on ebay hehe. came up that I had a bad ground point behind the intake runners.
going further I replaced all EGR hoses except thick back pressure hose which I will be replacing next week regardless, just to be sure.
also regarding EGR VSV. again I was wrong (this system is crazy and illogical at first glance):
"The VSV’s vent filter (...) prevents EGR operation whenever it vents off EGR control vacuum." from article #1.
also when pulling vacuum on the EGR valve port (on top) it actually opens it and not closes it (which makes sense with quote above).
and 1 more quote to make it more clear:
"The top of the vacuum modulator conceals the vent filter for the internal vent(...). The two vacuum inputs are ports P and R. The modulator’s output is control vacuum coming out of port Q."