Are you negating my point? I'm not really sure? Your entire first paragraph doesn't seem to relate to what I said, though half joking, my point was, if your opponent is TOO much stronger than you, you don't learn much from them. Your point about a 12 year old challenger or faker level reflexes doesn't say anything in regards to that one simple point I made. So I'm not sure if your replying to someone else and me at the same time or something along those lines?
If I use martial arts as an example, you don't match a white belt against a black belt, ever. They always try to get something along the lines of white to blue belt. The reason is, that if your opponent is outperforming you to the point then you can't even comprehend what it is they did to beat you, you won't be able to improve much as a martial artist and will more likely give up.
Same applies to school, teachers never jump straight into Physics until you've learn basic maths. You won't understand the benefit of space fold over FFL even you don't know the requirements on FFL (faster than light travel) which comes down to pretty sophisticated mathematical equations.
In terms of league, if someone is still learning how to itemise and which skills to unlock in what order, they will struggle to master counter picking, counter plays and the mechanics of poke vs burst vs sustain etc.
If someone has not got the grips of 1 v 1 laning, they will struggle to master team fights. My examples are not great because I am no League Pro, but the point stands. You learn in stages, and if you try to jump to far ahead, you will struggle.
To be clear, I am not saying that silver 4 should only play silver 4, or even that a silver 2 will only improve against silver 1, but a bronze won't learn anything in a game against a Gold, and gold is unlikely to learn much going up against a diamond, Because you will lose so hard you won't be able to isolate what you did wrong. Or things you did right you might think you did wrong because they didn't work. Maybe your last hitting was perfect, but you lost in farm due to lane freezing? Maybe your item build was great, but lost in damage because of the timing of instigations, or the enemy always poked you when you went to farm and kept out of your range so you couldn't poke back.
Until you've mastered "your" level of play, you shouldn't try to skip 2 or 3 levels because you won't know what's going on, except for occasional exceptions of course (like people who are better at map awareness than trading might have better decision making even if they lose in 1 v 1 or lane phase)
I hope my point has been made more clear. and you if still disagree, please try to keep your arguments in the context of what I've said or i may go completely off topic with my rebuke