Even if it was initially a bug, Hello Games now treat it as an official mechanic. One of the patch notes during the Expedition update (3.37, I believe) calls out "fixed an animation bug when melee jetback boosting." It seems HG has been well aware of this for many years and explicitly don't intend to remove it.

How the mechanic/glitch functions has actually changed over time, which indicates to me that they've deliberately meddled with it for balance purposes. It used to be, for instance, that if you melee-boosted into water from land or the air you would keep your initial forward velocity in the water and could "coast" at that speed as long as you kept holding forward and did not hit anything... even without jetpack input. This is no longer the case, which is a bummer because it made traversing large stretches of water less tedious. It also completely obviated the need for a Nautilus unless you were planning on diving, though, which is probably why it was tweaked. IIRC that change happened with the Abyss update, or whenever it was they changed the water effects to allow for the large waves during storms.

They apparently did patch one where you could normal punch boost but then keep meleeing, and just keep gaining speed in midair, and straight-up fly! Never got to try it out, it sounds like it was fun. But to be fair that one was just absolutely busted. This one isn't that much faster than the normal punch boost and it's way harder to control (unlike the flying glitch I assume).

-- Frost

Yeah! It's beautiful here. In the daytime the sky is mint green and it's really pretty.

There are "storms", but they just make the bubbles whip around really fast. Doesn't trigger hazard protection. You do have to watch out for the localized gravity storms though!

-- Frost