I agree with your interpretation however cameras DO lie (lens aberrations, reflected light etc.) When you slow that image right down in a movie clip editor it looks as though only some kind of vapour or liquid trail could have caused it. As you say, the odd thing is it's not detailed in the report. Since we could never determine that, the next question is "If it is fuel/vapour then where might it have come from?" And the next question is "How might that have affected the performance or the pilot?"