NCHAR is converted to DDesc.STRING(length,2000,false,true, false), which is variable length. It should be fixed length.
RAW is converted to DDesc.STRING(length,length,false,false, false), but it's binary, so should probably be converted to DDesc.BINARY(length, length, true)
EDatabaseOracle.createColumn()
Should convert DDesc.BINARY to RAW if it's <= 2000 bytes
Fixed in 13.0-rc-4