According to this article, a horizontal stabilizer runaway on the 737 MAX, unlike with all other 737s, cannot be countered with yoke inputs:
Older 737s had another way of addressing certain problems with the stabilizers: Pulling back on the yoke, or control column, one of which sits immediately in front of both the captain and the first officer, would cut off electronic control of the stabilizers, allowing the pilots to control them manually.
That feature was disabled on the Max when M.C.A.S. was activated — another change that pilots were unlikely to have been aware of. After the crash, Boeing told airlines that when M.C.A.S. is activated, as it appeared to have been on the Lion Air flight, pulling back on the control column will not stop so-called stabilizer runaway.
Why would the addition of MCAS require removing the yoke trim override mechanism? In the event of a trim runaway, the pilots' first reaction is going to be to pull (or push, depending on the direction of the runaway) the yoke, and requiring them to perform a separate, different action in the heat of the moment to disable the autotrim mechanism is an unrealistic expectation; allowing yoke inputs to cut out the autotrim relieves the pilots of the burden of having to recognise the problem as a trim runaway in order to solve it, and allows the problem to be solved in the same manner as other unwanted pitch excursions (by pushing and/or pulling on the yoke(s)).