A useless gimick coupled with specious marketing hype.
"The battery is good for 75 hours of run time, which is sufficient for two years of use."
"Riding your bike in the summer (even if parked inside) is enough to charge the battery so that it will last all winter."
"We designed a light that will last for years, while others only last a few months."
Some facts:
Solar panels that size are capable of generating only micro amps of current. 1000 microamps = 1 milliamp. 1000 milliamps = 1 amp... It would take such a solar cell well more than a year of full time sunlight to fully charge a AA size battery.
Any light with a battery of that size that lasts for 75 hours, is of little use on the bike to see anything with. Look at the useful time on other lights. They run a couple of hours...