It'll almost certainly be like the other Mack Extreme Spinners which means it will be a dampened, free-spinning car. The coaster has no way to lock direction or control rotation with any specificity during the course. The car rotates as dictated by the forces the car experiences. What makes it not "truly" free-spinning is twofold:
- The car's rotation is dampened fairly substantially meaning that, unlike, say, a nearly-entirely-free-spinning teacups ride where natural, mechanical friction is essentially the only thing that slows/inhibits rotation, the cars have adjustable dampening in their rotation mechanism that enable the amount of force required to initiate/maintain a spin to be adjusted. On the existing Extreme Spinners, rotation is dampened pretty severely—you'll never see any of the existing Mack Extreme Spinners quickly spinning anything like you'd find on a spinning Wild Mouse, a tea cups ride, or the like.
- Magnets can be placed at points along the ride's course to encourage the car to spin. This is very similar to how the S&S 4D FreeSpins can have magnets placed along their course in order to attempt to induce a flip—just on a different axis. The easiest place to see this in action is immediately after trains depart the station on Time Traveler. Left to its own devices, cars would remain completely still until the ride's first bank/turn. Instead, magnets are employed immediately after trains depart to induce some rotation prior to the vertical drop.
Despite this not being a true, rotationally-controlled coaster like Fast & Furious or Cosmic Rewind, no one should be worried about a debilitating-for-the-average-guest OR a boring-for-the-average guest degree of spin. It can be tuned and, on the existing examples, Mack has managed to do so very effectively.