No car I've ever driven, either on roads or tracks, or in sims, will spin from understeer if you brake. The weight transfer CAN bring the tyres 'back into the traction circle' or they can cause more loss of traction, but in either case something must be fubar on your car (or you can't drive very well) if it spins. The most that will happen is the car will 'tuck in' and tighten it's line (assuming the weight transfer helps you not hinders you). I suppose if you didn't move the steering wheel for a good couple of hours you
might spin but any normal person would be adjusting the brakes, throttle and steering constantly, and it would be EASY to stop it.
Lift off oversteer is a different matter, and is only compounded by braking.
Perhaps you were just going WAY to fast in a hatchback, understeered because of the hugely excess speed, braked because you've never read about driving, and got extra lift off oversteer. But if you did that (and I'm guessing you didn't because you'd have said) then it shows a complete lack of driving talent. Stamp Collecting might be more suitable.
So 'normal' understeer will never ever result in oversteer after braking if you have even seen a car, and lift-off oversteer recovering from a complete loss of mental ability to judge corner speed might be made worse. But lift off oversteer is only a famous issue in hatchbacks, and normal physics don't apply to them, only Supermarket Physics