Okay, read-only would be back to the FT81x documentation.
I saw this before and just hooked up my Logik Analyzer again to verify it,
EVE does not respond at all on the SPI during reset.
BT815_startup_01.png : just zoomed out from the end of the Power-Down Delay to the first couple of responses
BT815_startup_02.png : zoom-in on the first access with CLKEXT, CLKSEL and ACTIVE
BT815_startup_03.png : zoom-in on the SPI traffic before the first response
BT815_startup_04.png : zoom-in on the first two responses.
The first answer from EVE is the 0x7c my code is waiting for.
After that my code starts to read REG_CPURESET and the answer is 0x02 which means that the touch-controller is not done resetting.
Looks a bit like it EVE is locked but then at least host commands CLKEXT, CLKSEL and ACTIVE are working.
This makes me wonder what happens if I send EVE more host commands right after ACTIVE.
But then, it works now, no need to break it on purpose.