What would you consider to be a bobber with an xs,as the original bobbers were harleys with all the weight cut off them to try and keep up with triumphs,an xs bobber could only be like the brat style of bike,which again is like a follow on from what I would term a lowrider,still got suspension, without suspension it would be a chop or chopper,or perhaps I'm to old for these new terminoligys.
there seems to be no discrepency in the terms, cafe racer and flat tacker but a huge discepency in the terms bobber chopper and lowrider although you don't very often hear lowrider anymore,unless it's a car.