[Aerkuld]

If the grooves are original I wouldn't touch them. The factory probably put there for a good reason.

Although you get a high pressure jet squirting out of that groove, the actual flow is probably very small as a percentage of the pump flow and the effect on the overall oil pressure from that will be minimal.

However, for the oil to get to that groove it has to be finding a path from from the high side to the low side of the pump. You will get some leakage here anyway as the rotor has to have face clearance to the pump housing and cover plate of course. If the clearance is too high or if the faces are badly scored this could have a more dramatic effect on the oil pressure. That might be worth looking into.