@lewm This is from the manual on the DV505.
Horizontal balancingMain arm is designed to maintain itself always level. But horizontal balancing is still necessary to distribute bearing load evenly and thereby realize best trackability. To achieve this balance, shell and sub weight alone normally suffice. First position sub weight A closest to the fore, or sub weight B at white-color balancing point mark, and then slide sub weight on scaled bar by one notch backward per every 5g added to cartridge weight. (In using any shell other than one supplied, add to or deduct from cartridge weight the difference in weight between these two shells.)
It's a bit confusing, but it essentially references how to set the counterweight on the main arm wand. It does have to be set, and you will see some travel on the primary arm wand in the vertical plane, but it's very limited. If a bearing was not there then why would you have adjustment of that large counterweight?