[HelloNurse]

  >  I've been thinking about the futsal effect - which is how Brazilian footballers developed superior skills through a constrained small-sided game with 5 on each side, then moving onto a full football game with 11 on each side. My understanding is the constraints are designed such that the most important and difficult skills are trained in a fast, immediate feedback loop.

You might be underestimating how being one player in 10 rather than 1 in 22 and being never far from the ball makes every player more than twice as involved in the game, yielding more intense training than a normal game: feedback loops become more frequent, but not faster. For even greater intensity it is possible to play football with even smaller fields and teams, and in a cage to reduce interruptions.

This has nothing to do with iterations of the kind found in software development, which are about products and external constraints, not about training for individual skill and collective coordination.