Each of those "angular contact" bearings is only designed to withstand thrust in one axial direction, so they are used in a back to back pair, ideally with some controlled preload. If they used only one such bearing, there would be some unhelpful backlash.

Yes, there's some problem with the page timing out due to this bad gateway issue. Must be driving Lee round the bend! Make sure you copy the message text before trying to post it!