AIS B injuries are sensory incomplete AND motor complete. To be sensory incomplete, one must have sensation in the lowest sacral segments. This can be met in two ways: (1) light touch or pinprick preserved at S4-5, OR (2) deep anal pressure. To be motor complete, one must not have voluntary anal contraction AND no motor function more than three levels below the neurological level of injury.
The example you outlined (no VAC, 5/5 T1 MMT, sensation intact to T11, 0/5 MMT in BLE) is an example of an AIS B injury. Assuming strength and sensation are normal above T11, the person would have a neurologic level of injury of T11. All muscle groups below T11 were 0/5 and there is not voluntary anal contraction – making this a sensory incomplete injury (AIS B).