Well a lot of CD's swapped out loudness (amplitude) for dynamic range and really they aren't much better than vinyl. So there's a bit of truth to it. A properly mastered CD is far superior to vinyl in a technical sense. Not being an audiophile though I don't mind either as long as the record ain't scratchy and it's not a cheap deck with crappy electronics. Obviously the best "sound" is in the ear of the beholder and some people prefer the sounds of their child/teen years to a higher fidelity version available on CD.

Let me translate to what they are trying to say: "the dynamic range in the music mastered for vinyl sounds good".

Yes, by buying a vinyl record from the 70s (especially from renowned labels), you're buying a sound that is free from the digital remastering craze of the following decades.

Is that really true though? If they have the original recordings (which have a much better dynamic range than vinyl) the digitally remastered ones can indeed be more true to the sound of the original recording.

They can be, for sure, but in my experience it's hit and miss. For instance, I believe the CD reissues of Living Stereo records (from the master tape) are very good. On the contrary, I once bought the integral of Hector Lavoe, remastered, and the sound was very disappointing, with excessive highs giving an unnatural quality to the sound. Whereas my experience with vinyl records from Decca/London pressed in the 70s is consistently good. If you're willing to experiment and take risks, you can probably find good and bad everywhere. I was suggesting a disappointment-minimizing path...