I like #3...
I think it's somewhat misleading to conclude flat tappets are 'weak'. This WAS offered as one possible explanation of a sudden surge of flat tappet cam failure a few years ago. There is a possibility cheaper materials were used, and might STILL be used in the low cost arena! You do want to buy quality lifters/cams. But when the smoke cleared it was the opinion of most manufacturers that the EPA requirements on modern
oil had eliminated certain components REQUIRED for flat tappets but NOT required for over head valve and hydraulic applications.
Oil remains an issue, you MUST use the right
oil/additives to ensure adequate lubrication. I use Shell Rotella and a can of STP myself...