how can we be sure that the pilot requested change in altitude to avoid weather? He asked to deviate left of the path and requested an altitude change at the same time. IMO the pilot would have asked for immediate climb if he felt that the aircraft was in danger and could be saved by climbing..
The key here was that he supposedly
asked for a deviation and FL change. If I need a deviation, I will take it and notify ATC after the fact. No different for a FL change; if I deem it necessary, I can invoke the magic words and just do it. Asking implies something desired rather than necessary.
The issue here is assertion of authority, which ultimately rests with the PIC. Working with/complying with ATC is part of the job in normal circumstances as it should be. When things are abnormal, I am responsible and will do what it takes to ensure that I get somewhere safely. In the end, it's my airplane.