I was really trying to point out that for a simulator the man doesn't stand on the bike like anyone IRL would.
Every setting in this game the character is leaned forward placing weight onto his wrists which applies his weight onto the handlebars.
This is why as you go over any little bump in game the bike endos. IRL this isn't the case (as much anyways).
I think the weight displacement is fairly accurate, and if you watch pro's play the game, they almost never go over the bars unless a mistake is made, just like real life.
There are a few reasons as to why bumps would be causing you to go over the bars. Before I explain, you have to understand that a game with no fake external forces will create an extremely realistic simulation, so realistic to the point where it seems wrong and broken. This isn't because of the physics, but our lack of ability as players. You want the bike to feel and react in certain ways because that's just how it feels in real life, but it's important to note that what you do in real life is muscle memory and pretty much instinct for most riders. When going through a rough section irl, you naturally move your body around the bike to compensate for the roughness. It's natural, you do it automatically, but nobody really has an understanding as to WHY you're doing it, you just do it out of muscle memory because that's what works.
In the game, the rider doesn't move freely on the bike. (Depends on rider settings) YOU as a player have to force yourself to do something that feels natural in real life, but feels unnatural in the game, and that's simply moving your rider. The unnatural feeling comes from having to translate those movements on to a joystick. You cant just lean back through a rough section for example. It will put more weight on the rear, which really just preloads the rear suspension and sends you flying over the bars even worse.
In real life, I challenge you to try and mimic the default rider position in mxs, and ride around a track. Try and keep your core as stiff as possible and don't move at all. It's impossible, you cannot hold on to the bike. No human is strong enough to hold on to the bike at a static body position at race pace. You'll be bucked around like crazy just trying to keep all your joints from moving freely. You may not realize but irl you're always changing your body position to keep your weight distribution where it needs to be for the situation. It's incredibly hard to explain but if you can grasp that then you should be able to understand.
For the longest time I tried to come up with settings that are "realistic" until I realized my idea of realistic was based off of feeling, not data. If a game "feels" real and you're using a game pad, it's not a proper simulation lol. At the end of the day, it's just hard to play true simulators with gamepads because of the amount of things you have to translate from real life into a controller that goes in your hands. Most "simulators" use magical external forces to try and simulate a real FEELING game, but you don't want it to feel real because you have to accept that your idea of real is wrong.
So most players are correct when they are telling you to just practice, because with practice comes muscle memory, which is when things like moving your rider body around in game starts feeling natural. For me and most pro's it's pretty much instinct to move the rider around CONSTANTLY to compensate for bumps and such, keeping the weight distribution where it needs to be at all times to prevent you from being bucked.
Hard to understand I know, I did my best explaining it hopefully it'll help.
If you have any questions lmk I'll try to explain