Teropa,
if you look at the 2nd previous landing at Congonhas (p 13 of the FDR) you will see that the crew armed Autobrake MED but then used manual braking as soon as WoW on 3. That seems to me to be a good idea.
I understand from a note on this thread that the same crew accomplished that previous landing at Congonhas (denoted "2nd previous" on the FDR). So it looks as if their procedure was to arm autobrake MED but intending to use manual braking.
If that is so, one wonders why they did not then do this.
If you intend to stop at all costs (as you are suggesting the main motivation would have been), and you have in any case planned to use manual brakes at WoW, then why not just brake as you intended? Spoilers or no.
I am wary of speculation into human factors such as you proposed. There are so many things that could have happened with human minds in this unfolding situation. And everything one proposes is based on assumptions which we also have no further way of checking. This is not stuff we can ever get to be sure about in this case. Nevertheless, I think it a very good idea for professionals to think through what they might do in such a situation. (I was very glad way back when, when I spun a C152 inadvertently on solo with about 20 hours TT during stall practice, that I had seen one demonstrated a few flight hours before. )
PBL