Whether you are received by Chrismation only or received by both Baptism and Chrismation differs in different jurisdictions, but mean the same thing. The difference is the application of "economia" (dispensation) and "akrevia" (exactness).
Reception by Orthodox Baptism and Chrismation is "akrevia" (exactness) because there cannot be completely valid Mysteries (Sacraments) outside of the Church.
Reception by Chrsmation alone is a recognition that the external form of your baptism (with water and in the Name of the Trinity) was OK, but the Chrismation fills the external form of your baptism with what was lacking in its content (i.e., Sanctifying Grace). So when you are received by Chrismation alone, you are receiving the Sanctifying Grace of Baptism also. This is called "economia" or "dispensation".