It isn't odd at all. Many patients continue to have positive PCR tests for a long time even after the infection is cleared. PCR tests merely indicate the presence of viral genetic material, not necessarily infectious virions.
So, I don't doubt the anecdotal stories of people getting false negatives with the at home. My coworker also took 4 and only 1 finally showed positive in the end.
Dr Michael Osterholm has covered at great length what garbage the rapid antigen tests are.