Military Primary vs SSR
First of all, I do not know the coverage of Malaysia's military radars.
Do we know if a primary pulse reached the location of the last SSR reply?
There could well be a considerable gap between the last SSR reply and the first primary returns.
While there may have been a series of primary returns, what evidence is there to tie those returns to MH370?
Or was it a smuggler or drone?
The Malaysian Air Force has not published the radar tracks. Most militaries would not as they do not want any opposition to know their capabilities -- or coverage gaps.
In the case of incapacitation, the a/c might run on autopilot until fuel exhaustion or CFIT -- or be brought down earlier by other failure modes.
If those primary returns turn out to be from MH370, we may end up with flotsam somewhere between Malacca and Madagascar. Finding the wreck in those circumstances will make the search for AF447 look easy.