Shouldn't riders be as skilled going slow as they think they are going fast?
I'm not quite sure what you mean. Riders should be skilled at ALL of the speeds they need to use, period. And you cannot become skilled at higher speeds without
practicing at higher speeds.
The reason I think slow speed work improves higher speeds is because most of the skills differences between riders is about the abilities to manage lean and feel traction changes. I'm sure high speed feels different than lower speeds and I'm sure the only way to learn about going fast is to go fast but improving lean and traction skills in any kind of practice will influence them across the board--I believe.
Managing lean at higher speeds is COMPLETELY DIFFERENT than managing lean at low speeds. At speed, the bike wants desperately to self-correct, stand up and go straight, and you have to apply real effort to countersteer and hold the bike down in a turn. At speed, the sensation of losing traction is different, happens at different times and in different ways, and recovering from a loss of traction works totally differently as well. I cannot emphasize this enough--it is very important.
As far as gyroscopic effects, I think it influences the front wheel to turn in the direction the bike is leaning but isn't powerful enough to influence stability.
No, that's not it, at all.
A bike under power, traveling fast, is VERY stable. Very, very stable. If you've ever played with a gyroscope, or a bicycle wheel, or some other spinning thing, you have probably noticed that it resists being moved. It doesn't want to rotate away from its current position, and the faster it's spinning, the harder it resists. Motorcycle wheels are large and heavy, and gyroscopic forces they generate are very powerful. Actually, if you just had 1 single motorcycle wheel on some kind of armature just spinning all on its own at 60mph, and you walked up to it and tried to turn it with just the strength of your own arms... I bet it would probably take quite a bit to wrestle with the thing. The geometry of the bike is really pretty sophisticated, and is designed to help us by doing a lot for us. The wheels interact with the rake of the front forks in such a way that the bike self-corrects-- when the front wheel is turned, it wants to straighten out again, and that self-correction force increases in strength the faster you are going. The steeper the rake, such as on a dirt bike, the weaker that self-correction force is and the less stable (and more nimble) the bike-- whereas a stretched out cruiser with its front wheel sticking wayyyy out to the front is harder to turn. The more power is being fed to the rear wheel, the more stable the bike is-- if you have ever gone down a steep hill, you may have noticed how much less stable the bike feels than it is when you're traveling uphill under power. I'm no expert on the complex physics there, this is just the overview from what I can grasp.
You could do a
circus act on top of a bike that's traveling at highway speeds. You can throw your weight around any which way you please. It won't budge. Without countersteering inputs it will only laugh at you and continue traveling in a straight line with great determination. Left to its own devices, with nobody touching the handlebars and the throttle open, a bike traveling at sufficient speed can continue in a straight line indefinitely all on its own. My photography teacher hit a huge pothole on the freeway once, so hard that it bent both of his rims and blew both of his tires-- but the bike kept trucking in a straight line, and he did not go down.
A bike traveling at speed is a totally different machine. It behaves differently. It steers differently. It responds differently. Not just subtly different, but TOTALLY different. You cannot practice that without
doing it, that's like trying to fly a plane
on the ground.