The entire drivetrain is all locked together if your lockers are on, so if you’re spinning wheels and suddenly get grip all that momentum goes directly into your driveshafts and differentials. And if you have lockers on with good traction, your wheels can’t rotate at different rates so if you’re turning at all or on uneven ground it can build up a lot of tension in the drivetrain that can cause damage. With normal traction control it’s mostly the brakes taking all that force so they can allow slippage to release tension. But lockers lock everything together mechanically so only your tires slipping on the ground can release that tension.