Sorry, you have your facts wrong. Until 1972 the US had a huge grain surplus and almost all the wheat was Yashan. In ’72 the US began seling large quantities to the USSR and depleated the carryover from privious years. Since then, the majority of wheat in the market, except for winter wheat, is Chadash.
Furthermore, the Rema’s heter, really from Teshuvos HaRosh is based on an intersting sfek sfeika. Since today this information can be easily clarified, as Rav Herman does, one may no longer rely on a sfek sfeika (which anyways is not relevant when the majority is Chadash).