I wonder if it might be that size to cater for multiple teams? They talked a lot about having very personalised game day experiences for the clubs who use it.
Maybe they have dedicated change rooms? Dedicated function rooms etc?
Not sure about change rooms. You could be right though but I doubt they'd build separate change rooms for Wanderers and Eels.
I think it's more about the LED lighting and stuff like that, which they can customise to the game day teams. Check out the video I just posted.