See, you say that, but you don't really support it with evidence. Stress doesn't handle itself as well in very small groups in my experience, and to just shrug and say "well, the rules don't say I need to care about that" seems disingenuous.Um, no. The GM should not be considering stress available at any point. The system works out well such that stress handles itself
Taking account of available stress may not be in the GM's job description according to the book, but I like to run a game that's fun for players, and a player whose character is constantly accumulating traumas probably isn't having all that good a time.