Why can't I write to some Read/Write locations of the Triple-Speed Ethernet Small MAC Command_Config Register?

The Triple-Speed Ethernet MegaCore® Function User Guide incorrecly states the following locations of the Command Config Registers as being RW (Read/Write).

The register locations listed below are only RW for the full MAC configuration.

When you use the Small MAC configuration, these registers are R (read only) due to the reduced functionality offered by this variant of the IP.

i) PAD_EN (read back as 0)
ii) ETH_SPEED (read back as 0)
ii) LOOP_ENA (read back as 0)
iii) MAGIC_ENA (read back as 0)
iv) SLEEP (read back as 0)
v) NO_LGTH_CHECK (read back as 1)