I think there might actually be a famous writer who said "Steal from the best." But I'm not stealing today. Today I'm thinking hard about this, by one of my all-time favorite writers, Anne Tyler:
All really satisfying stories, I believe, can generally be described as spend-thrift... A spendthrift story has a strange way of seeming bigger than the sum of its parts; it is stuffed full; it gives the sense of possessing further information that could be divulged if called for.
That's the ticket. It could be divulged. As long as the writer knows the backstory, the character's history, what happens off-stage, readers don't need every single detail spelled out.