Is rated current supposed to vary based on voltage?
There are two aspects to the maximum allowable voltage specification a given resistor has.  One is the packages' power dissipation rating, which for a given value of resistance will have a maximum applicable voltage before heat dissipation values are exceeded: P=V^2/R

The second is a safety persective because the smaller the package the closer together the two terminals are.  Eventually the electric field gradient between them becomes so strong that you can get electromigration effects, tracking, etc. that will cause a short across the terminals.  There is a corollary in that post manufacture cleaning of boards becomes more critical as well, debris tends to become conductive over time with some soldering techniques.

In the case of the jumpers, Vishay RCCe3 series does have the voltage rating, could be the other datasheet is just missing the row (typos in datasheets happen all the time, most get caught some don't.)