the pressure comes from resistance to flow (volume) so a "high pressure" pump would merely be one that puts out more volume, the other factor would be the pressure relief setting of course. You can't make a low volume pump "high pressure" without limiting discharge flow. If it is putting out more oil than can be rejected by the various losses throughout the engine you will get higher pressures. And one of the main reasons for so much oil flow to racing engines is to pull heat away from the bearing surfaces, the actual lubrication requirement is quite small.