You need to realize this problem before it is too late. If there is full trim down when you realize it there might not be enough room left to offload the stabilizer and trim back (manually, no less). Afaik if you cut off stab trim you can only trim back manually by moving the trim wheels.

I'd not be surprised if there will be another problem with MCAS detected with the ET flight where the pilots had effectively no chance despite knowing of the Lion air crash.