The MAN 737 fire was somewhat more complicated than you state although I broadly agree with you. It was this incident that brought about the mandatory installation of floor level emergency lighting of aisles, indeed it brought about one of the most comprehensive reviews of aviation evacuation procedures ever. What was discovered during the investigation
afaik was that pax were disorientated due to smoke and fumes, this raised the issues both of materials used in seat manufacture and lack of any form of reference for pax when having to crawl down the aisles to get under smoke, I believe that it was found that those who got to the aisles clogged it by heading in opposite directions. There were other findings on which I am sketchy but the same situation would still be possible if those findings had not been acted on. The briefing was irrelevent as different situations appertained.
Hope I have not got this wrong and, if not, that it is helpful.