I think I'm as confused as maybe @pauly is... Do you mean put a shim (washer?) under the rose joint of the steering damper? This might help in some circumstances, but at least on my 1198S said rose joint attaches to a bracket which is welded to the frame. You can't shim that, and it is another possible/likely point of contact should the tank swell.
Ah, maybe the brackets on my 4 are bolted to the frame and can be shimmed forward, and your brackets are welded on?
Joking apart, why would the bracket be bolted onto the frame on the R bikes, and welded on the others? Maybe so you can shim the steering damper away from the tank...
Or an alloy tank, or just use a bit of persuasion on the welded bracket to move it. Actually riding them, what's better about a 1098R over a 1198 Corse?
It could be a "preparing for possible homologation" thing or maybe as said, leaving provision for a larger tank in the future.
No, a different league, full of Ti - over 200bhp possible with full system and Super Sport map - more torque standard too looking at the specs. Nothing wrong with a standard 1198/S/SP though the SP had a slightly better (read more refined) traction control and an Alloy Tank though.