You might be fine, but if any "pieces" were shed by the HPOP, they could be in the HPOP suction line or in the oil reservoir below the oil cooler. The procedure is to flush all of that to be 100% sure.Since the IPR screen was in perfect condition and nothing was on the screen, I would think the oil cooler screen is in good condition. I have a new one but I really don't want to pull the intake to change.
I doubt that anyone can give you any assurance that you will be ok by skipping that step. You might run that past the folks at DieselSite.