4 months on it is difficult to find the full Qatari govt rules that were in place at the time. Information on airline websites usually carries a heavy disclaimer anyway and double checking with a govt source is always wise, as is automatically assuming the worst case rules and strictest definitions will apply.

Maybe there was some other relevant information in this case, or perhaps there might have been a distinction between eu citizen and eu resident that was applied. And of course airlines are all very risk averse with grey areas these days anyway to avoid fines for transporting passengers ineligible for entry.

It sucks to be denied boarding for whatever reason, hopefully the OP was at check in early enough to avoid being classed as a no show. What are you hoping for from your correspondence with QR this long after it happened? Have you received a refund for the denied flight?