A consonantal script does not record how a text sounds. It records which consonants are written, in which order, and everything else, the vowels, the stress, the length of syllables, the melody of recitation, has to be carried by somebody who knows. In the Samaritan case that somebody is the community, and the knowledge is transmitted by teaching children to read the Torah aloud from people who were taught the same way.
That makes the Samaritan reading of Hebrew a piece of evidence in its own right rather than a curiosity attached to the text. It is independent of the Tiberian tradition that produced the vowel pointing used in Jewish bibles, and it preserves features that tradition does not: the weakening of the four throat consonants, the reading of the sixth letter as b, the reading of the seventeenth as f. Where the two traditions differ, the difference is data about the history of the language rather than an error on either side.
It also has the vulnerability of anything held in living memory. A manuscript can sit in a library for a thousand years and still be read; a reading tradition exists only for as long as there are people reciting it, and the Samaritan community numbers in the hundreds. Recordings and transcriptions made by linguists over the last century are the reason a written account of it exists at all, and the community itself remains the source those accounts are taken from rather than a substitute for it.