The osmo does not stabilize in the Z axis. That's the bounce you see.|
The cameras c.g is not in an optimal place to control all flavors of stabilization. This is why a full rig body worn stabilizer works well..its designed to pull the c.g. of the camera to the yoke/gimbal which allows the operator to precisely control x/y/z axis all from the nodal point (the gmbal in this case).
Even when wearing a full size stabilizer , you cant just walk regular. You have to walk a specific way to keep horizon bounce out of the equation. You have to stand a certain way, static and dynamic balance the sled, etc. that's the nature of these body worn stabilization systems.
Yes you will have to walk a certain way (you call it ninja) to minimize bounce in the Z axis.
Based on posts I've seen you comment in , you are well aware of the Z axis product DJI produce. It DOES help with the bounce and is worth the money if you want to get better images out of the osmo, but one needs to understand the limitations this tiny system has and work within those limitations.
With practice, you CAN get better images worth less bounce if you use the "ninja" walk. If you use the Z axis product, tune the spring properly, PLUS the ninja walk, i think you will be impressed at the images you can get.
Everythhing has limits, and yes this product is not perfect (no product on the market is). The key is learning the limits and working within them. Like i said in another post, its 90% operator, 10% gear.