Yes, per segment. The other poster is referring to the tradeoff; partner earning sounds attractive on paper but in practice, depends. There is a reason United added a cap after partner earning had started.

Economy fares usually only earn a fraction of actual distance (unless you buy a higher economy bracket fare, which may defeat any partner earning advantage in the first place). Same for PE and J, unless you can get a cheap premium fare, you might earn more on a United ticket, but then you might also be spending more in the process.