Yes, but 9.18.28.610238 is using diferent system folder (jp.pioneer.mbg.avicsync) from 9.19.1.483935 (com.nng.igo.primonextgen), that's why it's possible. Sharing of data folder is something else (iGO, iGO_NextGen, iGO_Avic, ...)
And yes, AvicSync (9.18.28.610238) is the best working NextGen version for now.