There are many errors I see in peoples' movement during flow -
1) They do not move at all - Sitting target
2) They move in a predictable rhythm - Predictable target
3) They only move in response to the opponent - Behind the timing
4) They move as though the opponent is not there - Dancing their own dance/Easy to hit
Not moving is only be a good idea if you can catch your opponent off their guard RIGHT at the beginning of an encounter, before they are ready .. or then momentarily within a movement flow. After that, movement gives you SO many advantages to exploit over standing still, and keeps you SO much safer, that it's a no-brainer to keep moving. Thing is, there is a way to move that makes sense, and many many ways to move that do not. Everything you do has to have something to do with what your opponent is doing, yet in cannot be as a reaction to what they are doing. It has to be unpredictable to them, yet connected to their movement. It has to make tactical sense, keep you safe, worsen their position, and limit their options whilst keeping yours as open as possible.
It's like dancing ..... yet with a somewhat different goal ... the demise of your dance partner.
It's a skill. It's important, and though it may become intuitive, it takes practice.
Tactical Hustle anyone?