You did not read far enough in the metabunk forum. A few posts accused them of not having a level laser. BTW a few dozen meters with one centimeter's error (or even one millimeter!) would not ensure a level instrument for projection across several kilometers. They would have needed to establish less than one millimeter variation over 300 meters, by checking in opposite directions, before they would have reasonable assurance of an adequately level laser. Then their accuracy would have been within 3 millimeters in one kilometer or 6 in two or 9 millimeters in three kilometers.
Unless it was a hoax, the measurements I saw on the video insured that the laser was adequately level. They were taken at many regular intervals, including ones very close by, and if anything the laser rose very slightly within the first couple interval measurements so that this should cause it to rise even more as you went farther. Posters on metabunk were simply saying what they wanted to be true. You're very emotional about this subject as well, so I do not trust your judgment either ... just as I don't trust the judgment of the people on metabunk. I'm seeking the truth in this matter and am not interested in emotional rants from either side. So, for instance, the evidence is almost irrefutable that 9/11 was an inside job and that the US moon landing was a hoax ... and yet you'll find tons of clowns out there trying to "debunk" the evidence and pretending to be objective scientists.
Basically, if the Hungarians were deliberately skewing the laser, they would have had an extremely difficult time creating the precise downward angle that would project itself into just a few centimeters at their farthest distance; they would have hit the water WELL before that point. They would have had to plan this out well before hand, do a pre-run a several kilometers out and then adjust the laser to hit the target FIRST and then come back and stage the experiment. Again, I am not ruling out a hoax ... where they did exactly that, but, absent a hoax, the evidence is very convincing.
Basically this works like a gun sight; if you can hit the first two targets precisely, then the subsequent targets are going to be in line.