I don’t want to get technical but there’s a couple of errors that you could drive a truck through on that video above that stands out;
1/ Flight directors initially command 8 degrees nose up through the take off roll and command a pitch angle based on speed after rotate. E.g V2-V2+15. The flight directors are independent of MCP setting and they do not sit at zero during initial take off as alluded to.
2/ The Flight director pitch angle wouldn’t/ should not changed after take off until VNAV automatically engages at 400ft if armed or another mode was manually selected prior to this point.
I think there might have been a bit more that went on other than what this very basic video has concluded, Be fair to the crew and let the investigation run its course.