Quite true. Even while streams are actively moving and chains are being completed and combos are happening, you can be dragging arrows around as much as you want. If you're quick and have a certain amount of experience with just seeing chains instinctively rather than with active top-level-brain-function searching, then you can set up all kinds of things after your streams have already been emitted.
That said, not everyone will want to do that, and certainly not everyone will have to, either. But if you ever find yourself just sitting around watching all the pretty colors moving and exploding... and wish there was something else you could be doing to affect all of that stuff that's going on... you certainly can affect it to an
enormous degree.
All that said, we try never to encourage the fast-clicky style of play over the more slow-paced Zen type of play, so certainly you can play in whatever style suits you the most.