Are refrigerated hard boild eggs really unsafe after a week?
Yes, they really are unsafe after a week.
According to the USDA (similar information can be found from other food agencies):

Why do hard-cooked eggs spoil faster than fresh eggs?
When shell eggs are hard cooked, the protective coating is washed away, leaving bare the pores in the shell for bacteria to enter and contaminate it. Hard-cooked eggs should be refrigerated within 2 hours of cooking and used within a week.

Simply put, you're damaging the shell, and that expedites spoilage.  Some secondary sources such as StillTasy (who use the agencies as their primary sources) are more liberal and say up to 2 weeks, but I'd at least give it a very thorough sniff test before eating hard-boiled eggs that old.  (And note that the sniff test will not necessarily alert you to bacterial contamination, only the more conventional forms of food spoilage like rancidity).