This might be a published fake FLAC file generation. Really, the only way for you to personally validate this FLAC compression difference is to buy your own audio file converter (such as Aul Converter 48x44) and compress some WAV files YOURSELF. Then test them and see if you can hear any difference. Not saying this phenomenon is untrue, just difficult to prove.
I know that there are some older media player software that just do not playback FLAC files with good quality. This has to do with having to uncompress the FLAC data on the fly. I think it was Monkey Media Player that really sounded crappy with FLAC files. I have had no problems with Jriver playing back FLAC and quality, soundstage, stereo imaging and depth has always been excellent. I know JRiver uncompresses "ahead" and caches data before it's clocked and sent to the DAC.
I know that there are some older media player software that just do not playback FLAC files with good quality. This has to do with having to uncompress the FLAC data on the fly. I think it was Monkey Media Player that really sounded crappy with FLAC files. I have had no problems with Jriver playing back FLAC and quality, soundstage, stereo imaging and depth has always been excellent. I know JRiver uncompresses "ahead" and caches data before it's clocked and sent to the DAC.