Then please correct me instead of giving indignant one-liners. Bonus points for including a source I can share to give better answers in the future.
Unlike Sierra (SSE4 CPUs) or Mojave (Metal GPUs) no new hardware requirements have been discovered, true?
Apple reported they were unable to patch the 5,1 for Meltdown and/or Spectre because of a lack of Intel microcode, true?
Apple chose to drop for the 5,1 from the list of supported models and block downloads/installs, true?
There might be additional reasons the 5,1 was dropped, but what if anything I posted was incorrect?