This may be an accurate conclusion for a standard product with arginine as the core compound. RPM is different. Arginine in RPM mainy serves to reinforce the synergy of the blend. In particular, arginine serves within RPM as a substrate for the enzyme nitric oxide synthase, necessary to stimulate the production of nitric oxide. Beyond this, OPCs in RPM also support nitric-oxide synthase, further enhancing elevated nitric oxide levels. As is well known, nitric oxide requires cGMP for effective vasodilation to occur. Enter icariin. By inhibiting PDE-5, the enzyme that breaks down cGMP, icariin ensures that elevated nitric-oxide levels triggered by arginine and OPCs are sustained by icariin-powered cGMP, creating RPM's well-known synergistic vasodilatory outcome. It is this synergy that allows a relatively small (yet effective) amount of arginine to be used in the formula. Anecdotal user feedback appears to corroborate this synergy.
Again, in a standard arginine-centered product, your observation may be valid. In the case of RPM, though, several considerations justify the choice. Firstly, standard L-arginine has the most amount of base arginine relative to the more advanced forms. Furthermore, some advanced arginine forms may not guarantee an adequate amount of arginine bioavailability and absorption. Secondly, the inclusion of naringin in RPM not only ensures a lower amount of base arginine can be used, but also supports absorption and bioavailability, and consequently, an extension of the half-lives of the synergistic compounds in the formula.