Correct. The pump is made of an aluminum housing and side plates, with steel gears. Many (most) tractors are designed this way, and are problem free with that design in itself. What usually hurts pumps is (1) heat and (2) contamination of the oil.
Hydraulic oil does 2 things (and then some) to the pump. It lubricates it and cools it. Cool oil going into the pump helps it live. Good clean oil (UDT or preferably super UDT2) keeps it lubricated.
Generally speaking, pumps should not be replaced without flow testing before AND after. And that means inspecting the supply pipes and filters for dents, suction leaks, screens, etc. When the pump is trying to "suck" aerated oil, it gets hotter than normal. Also, contaminated oil causes problems. Water (moisture) doesn't lubricate very well. Some cheap hydraulic oils have a tendency to develop algae in the oil, which causes filters to become restricted, thus causing wear on the pump. I have NEVER seen this happen with UDT or Super UDT (JD Hy-gard and the TSC oils are a totally different story...). Then if a loader valve or 3 point position control or other implement is not adjusted proper, and the system is constantly making maximum pressure (against the relief valve), the oil will overheat quickly and destroy the pump in no time. Like the time when a customer of mine had his M5040 running a hydraulic log splitter, closed center...when he wasn't using the splitter the tractor was making 2500 psi hydraulic pressure. Took less than 50 hours to destroy the hydraulic pump.