Yes that is true. Apple decided against DRM, hoping other online music companies would follow suit. But online iTunes music quality is still much lower than can be obtained from CD.

Have you listened to very loud music through a single wall? The wall filters out several of the frequencies & quality. Music sold online is roughly basically the same. m4a/mp3, etc. drops all frequencies above 15KHz & below 10 hz. Changes the actual structure of the music by adjoining similar frequencies, dropping some frequencies & boosting others, changing the music shape; this can be seen when comparing original with mp3/m4a audio bandwidth frequencies on a spectrograph.