Think back when you first got into digital photography - was all this stuff so immediately obvious to you, or did you have to read, learn, think and experiment?
In this instance, yes it was. Given that just about any color perceivable by human vision can be reproduced by altering the mixture of red, green, and blue color channels, it is totally illogical to think that altering one color channel by itself would not
affect the color balance of an image. It's fairly simple logic:
Premise 1: RGB images encode a wide range of colors by mixing various amounts of red, green and blue. You can change one color to another by changing the red, green, or blue color values.
Premise 2: Using the levels control on one color channel in an RGB image will change the color values for that channel compared to the other channels.
Conclusion: The levels control, when applied to a single color channel, will change the color balance of the image, because the values for one color channel are being increased or decreased in relation to the other two color channels.
Think back to the recent thread about polarized sunglasses. The original poster claimed to be familiar with the operation and effects of a polarizer, and said he knew that his sunglasses were polarized, yet was sufficiently amazed by the fact that the polarized lenses actually did what they were designed to do that he felt it worthwhile to post his "discovery" to share it with the rest of us. But again, simple logic should make that instinctively obvious:
Premise 1: Polarizers can reduce or eliminate reflections on water.
Premise 2: My sunglasses' lenses are polarizers.
Conclusion: My sunglasses' lenses will reduce or eliminate my ability to see reflections on water when I wear them.
I don't mind answering questions that indicate the questioner put some thought and effort into posing the question, but when questions are asked that indicate either a total lack of understanding of the most basic, foundational concepts, or (more often) a near-complete non-use of critical thinking skills, it makes me (and others) feel like the driving instructor whose student asked how wheels work. At some point, it becomes difficult to distinguish legitimate questions from silliness posted with the sole purpose of being annoying. I know people say there is no such thing as a stupid question, but that isn't true; there really are stupid questions:
"What's the number for 911?"
"Do you think I should let my kids sleep with Michael Jackson?"
"My stripper girlfriend is cheating on me. If I married her, do you think she'd stop?"
I'm sure nobody would find it particularly helpful or useful or relevant if I posted a thread about how the sun rises in the east or how rocks are a bad choice of lens cleaning implements; where do we draw the line? I don't hate anyone, the primary goal of what I write is to get people to think logically and use more common sense. A little bit of that would go a long way toward answering a lot of the questions posted here and elsewhere.