it's still super important to be able to keep your crosshair fixed on one place while moving and also be able to stop moving and have your crosshair on that same spot, decelerating your mouse movement as you stop moving
I don't see the point of practicing movement aim in an aimtrainer. It's completely different from the game anyways. imo it's much better to do it in game, even if you just load up the firing range or a map with some bots and aim at them. You'll have the exact movement, inputlag and feel of your game and you can practice other stuff there too like rocket jumps, projectile aim, abilities or whatever your game has. But the best way to practice movement aim is aim duels like LG 1v1. That will not only train your aim but also how to move to avoid being hit which is just as important as aiming.