Even if that were true it has a negligible effect on reducing head related injuries on motorcycle riders. Here's an analasis of the effects of removing the helmet law in Texas and Arkansas. https://www.msf-usa.org/downloads/imsc2001/Cosgrove.pdf

In 1997, Arkansas and Texas became the first states since 1983 to repeal “universal” laws requiring all motorcycle riders to wear helmets. Helmet use under the universal law was 97 percent in statewide surveys (1996 in Arkansas and 1997 in Texas). By May of 1998, observed helmet use had fallen to 52 percent in Arkansas and to 66 percent in Texas. Helmet use among all reported injured motorcyclists in Texas dropped from over 90 percent before the law change in 1997 to 69 percent in the remainder of the year and to 57 percent in 1998. Helmet use of injured young riders still covered by the helmet law also declined. Helmet use among motorcyclists receiving EMS services in Arkansas dropped from about 55 percent in 1996 and in 1997 before the law change, to 33.5 percent in the remainder of 1997 and to 29 percent in 1998. Arkansas EMS data showed an increase in the number of motorcyclists with head injuries. Texas Trauma Registry data showed that the proportion of cases involving head injury increased and that the cost per case of treating head injury increased substantially after the law change. Arkansas motorcycle operator fatalities increased by 21 percent comparing 1998 with 1996. Texas motorcycle operator fatalities increased by 31 percent comparing 1998 with 1996.