ksz884x: Why is advertising changed based on speed?

Does anyone know why ksz884x manipulates advertising based on the
value of speed instead of just passing cmd through to
mii_ethtool_set_link_ksettings() like most other drivers do?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/micrel/ksz884x.c?id=11dd894e4afa7995d8e4bd6008cbd79840c3a8bd#n5999

I am finding that if I do `ethtool -s enp3s0 autoneg` immediately
after bringing up the interface that it changes the advertised link
modes to 10baseT/Half since the driver apparently is reporting a speed
of 10 and duplex of 0 at that time.

If no one can site a reason for the driver doing this I'll be happy to
send a patch that removes it.

Thanks,
George McCollister