The short answer is NO. The Encoded 10-bit character stream is achieved by setting ENCBYP* = HIGH and BYTE8/10* = LOW. The byte-packer is a logical construct, used to control the efficient segmentation of 10-bit source characters into 8-bit characters. This conversion allows these characters to be transported using 8B/10B encoding with the same encoding overhead (20%) as when sending 8-bit characters. Because the serializer continues to operate using 10-bit transmission characters, this encoding mode can only operate with the transmit FIFO enabled.
For more detailed information about byte-packed mode, please refer to CY7C924ADX datasheet (link attached), specifically Figure 4.
200-MBaud HOTLink Transceiver (Attached Below 38-02008_0D_V)