(Summary for the hopelessly illiterate (a.k.a. "tl;dr"): By your definition, no reveal trailer would ever be worth watching, because very few of them actually have gameplay footage unless they're mere weeks/months from release or releasing day and date of the reveal.)
(Now the part for those who can actually read.)
It's actually not too uncommon for a publisher to include something along the lines of "Version not final, does not represent actual game footage" or "All footage represents a game still in development" in game trailers before release. It's not really an indication that a game will be better or worse than what's initially shown. It's meant to both temper viewer's expectations of the final product (since things can and often do change between first reveal and full release), and potentially keep the publisher out of legal trouble if people attempt to claim "false advertising" based on any trailer prior to the launch/"Available Now" trailer.
The only thing that differs in most cases is where this message appears. For the Pokemon Winds and Waves reveal trailer, Game Freak/The Pokemon Company/Nintendo elected to put this both at the start of the initial cinematic, and then at the part that begins showing what could be mistaken as (finalized) gameplay footage. For the Monster Hunter Stories 3: Twisted Reflections reveal trailer, however, it's placed as this fine print at the
very end of the trailer (funny enough, this was the case for the reveal trailers for Wilds and previous Stories titles):
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Honestly, I find the implementation of the disclaimer in Winds and Waves more trustworthy, because it's GF/TPC/Nintendo letting us know up-front that the trailer is not fully reflective of what the final product will look like visual/gameplay-wise a year from now. Whereas Stories' disclaimer being at the very end could be seen as Capcom barely fulfilling legal obligations while simultaneously lulling consumers into false expectations and artificial hype (and we all saw how
that went with Wilds).
Alternatively, there is also a disclaimer indicating what platform gameplay footage was taken from, if what's shown in the trailer is actual gameplay (and not just footage that's altered to look like actual gameplay running optimally at highest settings - looking at you, Gearbox and Randy Pitchford). This disclaimer is sometimes followed with other parts that indicate if certain things were altered for cinematic purposes (such as camera angles) or if gameplay experience might differ in multiplayer. Helldivers 2 is one example of a game that had this kind of disclaimer in its trailers.
(Extra note: Oddly enough, this disclaimer is missing from most, if not all, reveal trailers for games developed by From Software - not even for The Duskbloods, which rules out the trend being a Nintendo/Switch-only thing. Maybe Fromsoft's just confident that they won't get sued even if something changes, or that fans will just take whatever's given to them.)
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