While it's true that a TU balancer guarantees full throughput regardless of how the inputs and outputs are utilized, it doesn't provide a similar guarantee for balance. The balance properties of TU balancers are the same as those of regular balancers. Inputs must be fully utilized to get input balance, and outputs must be fully utilized to get output balance. A 4-4 TU balancer with one input omitted, for example, would still balance output, but would no longer balance input.