I have gone and tested the Command Golem Affix and confirmed it is NOT working at all in Battlegrounds either! In a real Battlegrounds match it does not work at all.
However, I have been able to get it to work in Battleground TRAINING.
Entering the training match, with 4/4 Command Golem Affixes and using Wiltbloom Golem Suit, at the start of the match I can see that the 3rd Ability Soul Blast has default range, the same as if it had 0/4 Command Golem Affixes. But if Ichange Legendary Gear for one of the slots that has a Command Golem Affix to a piece of gear that does NOT have it, going from 4/4 Affixes to 3/4 Affixes, the +30% Size and Range buff from the Affixes now works! And if I then re-equip the gear with the Affix to go from 3/4 Affixes back to 4/4 Affixes, the Size and Range now receives the full +40% buff! It went from no buff at all with 4/4, change to 3/4 to get buff to work +30%, and change back to 4/4 Affixes for the +40% buff.
Obviously, theres no way to change gear in a real Battlegrounds match, so currently there is NO WAY TO GET THEM TO WORK IN BATTLEGROUNDS.