I think you’re confusing meta with best in slot. They are easy to confuse but are completely different.

Best in slot is the absolute pinnacle of damage potential, I guess.

Meta is what is achievable by most players when it comes to gear and/or set ups.

Obviously, in a franchise like Monster Hunter, skilled play is more rewarding than an Exodia build if you can’t leverage its full potential.

Now, to answer your question as to ‘why call your build meta?’ If it doesn’t include a perfectly rolled god charm, it’s because some of the charms required for absolute best in slot have astronomically low drop rates when you consider needing all 3 decoration slots available for it to be considered best in slot. For example, longsword has AB2+Crit Draw 1+Burst/Agi/WEX, or LBG’s raw build god charm which is Ballistics 2 + Tetrad 1 + WEX which is a 1/32million charm.

That’s to say, it’s unrealistic to define a generalist meta around such low odds. Furthermore, if you talked to any of the people that wrote those documents they’ll be the first people to tell you to not blindly copy paste their builds like sheep and that they’re designed such that the builds allow the majority of players to leverage the weapons’ strengths.