I agree, dirt kills bearings, but I have seen three of four of this exact plug out failures the die in 2-3 hours of run time. Motors built in clean enviroments. I can’t imagine dirt is killing these bearings in that short of a period.
You have other problems like too tight of clearance or not cleaning out the passages, A lot of guy bead blast parts and the glass gets stuck in the casting and wont come out till the temp comes up and then it goes through the pump, if its a cheap filter and the bypass opens at 8-10 psi then at high rpm's it opens and the glass exits the filter and trashes the bearings. I ran the same bearings for years and ran my 340 to 7600 and a few times to 7800 and the bearings looked like they did when I took them out of the box.
