Most dyno charts show this, and it seems common on a lot of bikes that meet Euro 4. I be that there is some testing happening in that range, and they need to control emissions tightly, at expense of torque. I'm still breaking mine in (500km so far), and eagerly await the time I can play in that flat spot
On top of emissions i think the flat spot on this bike is a deliberate rich area to lose power which makes it more ride-able
and controllable. As soon as you back off the throttle a little, the front end comes down.
Fix the fuelling in that area and it's a different story.
I've looked at pretty much every gsxs dyno curve. I've seen that flat spot on stock bikes and bikes that have full exhaust and custom maps. Haven't found a clear answer as to why it's happening.
Really wish it didn't have that flat spot since that's my lower rpm range when at the track and really need that power. I ended up having to change my gear choices and requires an extra shift. An bike life.