OK, let me see if I'm understanding this correctly.
You're simply asking that, if your JG doesn't gank you when you provide CLEAR and OPEN opportunities, and your enemy laner gets fed and proceeds to wipe the floor with them, don't blame you for it?
That's how it's coming across to me. Feel free to correct me if I'm wrong.
Now let me try to answer this other question.
First, if you're giving your JG opportunities to gank, whether in the behind/even situations that you list, and they don't take them, that is a CONSCIOUS CHOICE that particular JG player is making. It COULD be subconscious as well, though; they might not be paying attention to the mini-map, or Levels, CS rates, etc. They might not consider it worth the risk to save a "failing" lane. I'm NOT SAYING that being a Level or 2 behind means you're doomed to fail, they just might not consider the risks of helping a failing lane worth the reward, in comparison to the more appealing option of just getting another lane fed.
For example, if you were a level or two (Just speaking hypothetically) behind your opponent, your JG might see that and think to themselves:
"Crap, my top-lane
isn't doing so hot." (Just using Irelia as an example, don't know if you actually play her or not)
He or She might then look at your other lanes and weigh their options.
"Should I risk going top-lane to help Irelia, in the hopes that the enemy JG doesn't notice and take advantage to gank our Mid or Bot lane? Or should I help one of our other lanes to try and get them fed to make up for Irelia's shortcomings?"
Seeing your lower level, they also might think this:
"Irelia's down a level or 2 from her
(Once again, just an example) opponent. With that level advantage, he could be capable of taking and killing both of us if the gank goes badly, and just make things worse up there."
With that, they might think you're too far gone, and their time would be better spent getting the Mid lane or Bot lane fed instead. Now, I know that's EXACTLY the thing you're speaking against, but remember, this was just a hypothetical scenario.
Next, are you asking that Top-laners be given more WEIGHT, more solo-carry capability? I already mentioned above that there are certain top-lane champs that, when fed, have carry POTENTIAL. Meaning, if they can get fed enough, they can wipe the floor with the other team. Champs like
or
or
and even
. There are certainly more, but these are just examples.
We have to remember that League of Legends, like most other MOBAs, is a TEAM GAME. Now, LOL and DOTA2 might have more solo-carry capability than a game like HotS (Heroes of the Storm) but while solo-carrying IS certainly an option, it's not considered the PRIME strategy. If we were to give Top-lane more WEIGHT, it would mean putting an objective of something like Dragon or such up there. Something that would DRAW the attention of the JG, because, an objective of great potential is there, thus they would be more motivated to gank you, in hopes of securing that objective.