Buzz
I may be totally off your wavelenth, but essentially you are correct with the idea of a 'sterile' cockpit below 10k.
As a really old hand - rapidly approaching 70 - I run MCC courses that give valid yardsticks about cockpit communications and we do NOT subscribe to non verbal instructions.
Please PM if you need forther info. My background is 16 years RAF and a similar period on Boeing 737s. dbee