I've been hearing about starting in the middle, during action, etc. for almost my entire writing career. As is common during said career, I had to hear the right permutation of advice at the right time with just the right word before I could blow up a hidden weakness. Ah, those hidden weaknesses, how they plague us!
So thanks, David! Now I know. It's not about starting with action, really, not per se. It's not even really about conflict, which a lot of really great openings don't have. It's about the pov character in that opening friggin' doing something more interesting and challenging than picking nose hairs out, something that stands out in his/her/its day that's hard work or emotionally challenging.
Writing-Helpful Trivia/Word definition of the day:
Climacteric: Pertaining to or constituting a climacter or critical period in human life; critical, fatal.
2. A critical stage in human life; a period supposed to be specially liable to change in health or fortune. Some held all the years denoted by multiples of 7, others only the odd multiples of 7 to be climacterics; some included the multiples of 9.