Not being able to choose your move seems to be a core feature of TMs, but complete randomness is not necessarily the only way to implement it. They can also be implemented simply by shifting move's index position +1 every time it's used, preventing the back-and-forth cycle but at the cost of guaranteeing the use of multiple TMs for some cases. For example, Melmetal's Charged Attacks, in the specific GAME_MASTER order, is Flash Cannon, Thunderbolt, Hyper Beam, and Rock Slide. An index shit would always guarantee Hyper Beam -> Rock Slide or Flash Cannon -> Thunder Bolt in 1 TM, but Rock Slide -> Thunderbolt will always take 2. So the question is, considering how Niantic is constantly expanding existing move pools, which is a preferred way to implement TMs?