Was the Distinguished Flying Cross awarded on a basis of number of missions flown, or reserved for specific incidents of distinction?

Greeting Indy,
My grandfather was a navigator on a Lancaster bomber with the RCAF based out of Britain, and he received the Distinguished Flying Cross on December 1st, 1944. He refused to speak about the war until the day he died, but he did keep some memoirs for the family to see after he’d passed, including what appears to be the recommendation for the DFC. It lists a number of very general things and the number of missions he flew, but when doing the research to have his medals properly arranged, my aunt was told that the DFC was an award for specific moments of distinction, no simple pat on the back for continuous good behaviour. Part of me has always wondered if this is worth additional scrutiny - if maybe the real reason he was awarded the DFC was something that was kept secret at the time and that this fairly generic recommendation is a cover for that, but part of me says it’s just what it says it is on the tin.

If you would like a more detailed list of what was given for the recommendation, I will seek permission of the rest of the family to provide more specific information. (I’m not sure how my mother and her sisters would feel about me digging into their father’s history, especially a part that he deliberately held back from them for his entire life.)