Correct. And the poster never claimed this.
It will protect you against a single drive failure in an array (RAID5) or two drive failures (RAID6). It works well. Plus, muliptiple striped disks are a lot faster, if that matters for users.
Frankly, for the extra cost, I see no point in a NAS unless you can run RAID on it (even running RAID1 with two disks is worth it for the cost, compared with the cost of the inconvenience if a drive fails).
Having spent 10 years as SVP of Engineering for a company making petabyte storage systems which had no single point of failure, we gave the same message - you still need on-site backups and off-site backups (plural).
At home I have two RAID units (domestic ones) and both are double-backed up (they clearly both risk multiple single point of system failure).. In the last 14 years, I have had a single HDD become totally dead, and two that got flagged as "struggling". Easily replaced, but long build times, during which time a RAID5 unit is vulnerable to another drive failure, but the statistics are in your favour. Nevertheless, if you have two copies of the affected drive or data, you are usually OK. One of my RAID units spent 5.5 years travelling about in a caravan that was my only home - zero issues - and that was HDDs, and not SSDs which at the time were not cost-justifiable for me. Still not, for my bigger 24TB main system! Although I only use SSDs for individual PC drives, and for TV etc.
N.B. music is only a small part of what I store. We used to have 7 PCs in the house, all boot-image backed-up as well as all the data drive content from them.