I have replicated the following behavior with MP 1.3.62 and 1.3.66…
When installing firmware (using ArduCopter v3.6.8) I reply “No” to the “Upload ChibiOS” prompt because I want Nuttx installed. However, even though I reply No to this question it is installing ChibiOS instead of Nuttx. The prompt works correctly on previous firmware version installs, allowing me to flash with Nuttx. However AC 3.6.8 firmware refuses to take No for an answer.
Has Nuttx been completely eliminated? The fact that there is still a prompt giving us the option leads me to assume that I still have Nuttx as a choice of OS.