In TLS 1.3, we dropped the "ecdh_" prefix on ecdh_x25519 and ecdh_x448 when we split signatures from NamedCurve/Group. The documents should probably match in naming one way or another. I think plain x25519 and x448 is tidier. X25519 already denotes the ECDH function, as opposed to curve25519 which is the curve.
(@ekr suggested I file this here.)
In TLS 1.3, we dropped the "ecdh_" prefix on ecdh_x25519 and ecdh_x448 when we split signatures from NamedCurve/Group. The documents should probably match in naming one way or another. I think plain x25519 and x448 is tidier. X25519 already denotes the ECDH function, as opposed to curve25519 which is the curve.