I still don't believe an ETOPS airliner can have BOTH engines display the same behaviour at the SAME time due to fuel freezing or boost pump contamination.
Doubtless your concern is not yours alone, which is perhaps one reason we don't have "the answer" from the NTSB yet. But keep in mind the current theory isn't just "fuel freezing". That is only part of the problem.
The current theory runs like this: during cruise the fuel flow was fairly light and equal, and both lines iced up about equally. Not enough to starve the engines, but enough to restrict flow to about the current flow.
Now the plane descends and warms. The ambient is warmer than the fuel, and the line going down the engine support is quite warm on the outside. The ice begins to thaw nearest the tubing wall, but is still frozen inside. We now have a lot of "loose" slush, but because it is impacted and has minimal flow past the inside (and thus minimum pressure exerted on the ice mass) it isn't going anywhere.
Now the plane has to counter some ground turbulance, and as it just happens, this results in three cycles of rythmically increasing and decreasing fuel flow. You may have experienced how one push on something stuck won't get it lose, but if you push on it rythmically a few times you will eventually get it lose. This isn't just your imagination; there are well-understood reasons why this happens. The theory seems to go that this has broken lose the ice in the lines, and probably got some (but not all) of it down to the heat exchanger.
Now finally there is a call on both engines for massive fuel flow compared to what has gone before. This causes all the ice to break loose and pile up against some obstruction, resulting in a major blockage. It is possible this obstruction was the heat exchanger. It is possible that it was some place upstream in the fuel piping that has not yet been identified. The result would be approximately the same, but not identical.
So there is a solid theory, based on both physics and experiment, that can (almost) account for the observed symptoms in the crash. There is also a demonstrated way (blocking the heat exchanger) that
could cause this result. So there is reason to fix the heat exchanger post haste. The problem is that blocking the heat exchanger doesn't quite account for
all of the observed symptons. So they can't say "fix the heat exchanger, case closed". More research is unfortunately needed, and probably solutions to other problems once they are discovered.