Without starting a discussion about the disadvantages of the not interconnected sidesticks, but do you have a source for that statement, any statistics, etc.?
The data available are only incident reports. Dual-input caused hard landing/tailstrike are prevalent mostly in cases where the Capt is PM and I could find only 30 such events. However, many reports are still pending in the preliminary stages. Most of the landings between 1.7G-1.85G is not a reportable occurance. So the data is scarce. I'm only quoting from logic and experience.