Firstly, what you're arguing against is not meta-gaming, it's forcing an outcome. Meta-gaming would be viewing the game as a game, and forcing an outcome is distinct from that.No, the burden is on you to try and defend meta-gaming. Extraordinary claims require extraordinary evidence. Where does it say that the DM can (or should) alter anything about the world, to force an outcome based entirely on personal preference?
Secondly:
1st Example: Ignoring the Dice, pg 236 of the 5E DMG:
"One approach is to use dice as rarely as possible. Some DMs use them only during combat, and determine success or failure as they like in other situations. With this approach, the DM decides whether an action or a plan succeeds or fails based on how well the players make their case, how thorough or creative they are, or other factors. For example, the players might describe how they search for a secret door, detailing how they tap on a wall or twist a torch sconce to find its trigger. That could be enough to convince the DM that they find the secret door without having to make an ability check to do so. This approach rewards creativity by encouraging players to look to the situation you've described for an answer, rather than looking to their character sheet or their character's special abilities. A downside is that no DM is completely neutral. A DM might come to favor certain players or approaches, or even work against good ideas if they send the game in a direction he or she doesn't like. This approach can also slow the game if the DM focuses on one "correct" action that the characters must describe to overcome an obstacle."
2nd Example: Rule -5, Obvious, no quotation necessary:
The DM can do whatever they want with their game, as the game is inherently flexible. Show me where the DMG forbids a DM from forcing an outcome. The DM is not barred from doing anything. Whether those things should be done is another question entirely. Given that I agree with you on the basis that I prefer a much more impartial and natural DMing style, I'm not sure why you've decided to focus on me.
You will notice that the quoted example discourages having only one correct condition, but not having all conditions lead to a success.