I just checked out the Honda press release that noted all the changes to the drivetrain. Here's what was said regarding the flywheel and the transmission. No upgrades to the clutch were mentioned.that its a different clutch disk since the flywheels different
A new single-mass flywheel is 26 percent lighter than the dual-mass unit used in the previous Si. The flywheel’s 30 percent reduction in inertia gives the 1.5-liter turbocharged engine a snappier throttle response for an even sportier driving experience, while also improving drivability. To maximize available traction when accelerating, power is routed to the front wheels through a standard helical limited-slip differential.
Equipped exclusively with a manual transmission, Si’s 6-speed has been updated for enthusiast drivers with improved shift feel and 10 percent shorter throws. A new, more rigid shift lever mounting bracket and a new leather-wrapped aluminum shift knob similar to the Civic Type R’s contribute to the improved feel.