Believe me, they are still all downloading all at once when you enter a Hub. My harddisc is really loud, I can hear when something is downloading. (Don’t ask, it was cheap 
)
You can also tell by the fact that you can switch portal views immediately once they are all loaded.
So i guess its only a client hardware concern.
Which brings me to another issue: They don’t seam to care for any priority while downloading. I have to wait a lot in hubs because other portals load before the one I’m looking at.