No there isn't. You twisted argument to be an absolute when it wasn't. That makes your response a Strawman. Don't do that.
And again, compare your initial stance "It sees you unless something special happens to keep it from being seen" and what I said which does not require something special to happen: "Again, if I try to approach someone from 100 feet away, in darkness while he is engaged in combat, will you pretend that the rules say that he will ALWAYS see me ?" Because nothing special happens, it's just a situation that happens reasonably often in combat.
So don't accuse me of strawmanning either. You have a very extreme attitude on this topic which again is not invalid if that's the way you want to play the game, but please don't try to imply that other people are wrong according to the RAW by not accepting that all creatures in D&D have an unfailing sense of everything that happens on the battlefield better than any real world individual or "better than military special forces and olympic athletes". This is not strawmanning, these are your exact words, and I don't think that many DMs would accept these premises as a basis for their games if they want some verisimilitude.
LOL There you go declaring people who disagree with you about how the rules are written, "gamist" or "powergaming" again. Sorry man, but if I'm "gamist" for arguing what the rules say, then so you are you.
No, the problem is that you are inventing things that are not in the rules to try and force a gamist attitude (which, by the way, I've never said anything bad about) on the game when I'm just pointing out that the game, in itself, out of the box and perfectly RAW supports completely different ways of playing and that these are not worse for being different from your specific perspective.
The game never says that you notice anyone casting a spell, just as he never says that you notice someone talking in the middle of combat, despite the volume of noise generated being the same, or not. The game never says that you notice someone doing a gesture with hand during the combat whether it's casting a spell or scratching his bottom. It's all in the descriptions of the DM, who has the absolute right to say that a given character notices something
or not based on the circumstances.
The gamist attitude that you propose is a valid way to play, but not more valid than the opposite attitude that fully empowers the DM to tell exactly what he thinks a character sees based on the circumstances, that's all.