Of course it isn't. If you say "sectors" why would it be blatantly obvious that you really mean "clusters of sectors"?
In today's reading comprehension class, we'll look at the original claim, which was:
They track sector-level accesses and automatically move "hot" sectors to fast storage - without any knowledge of "files".
Note that "track sector-level accesses" is inherently independent of any higher level clustering. If, as volume managers should be doing, you're looking at accesses at the sector level. Perhaps you're mapping those sector accesses to clusters of sectors - but you're still "tracking sector-level accesses".
The second part, "move 'hot' sectors to fast storage" similarly is true regardless of any clustering. It's true even if you move a few adjacent "cold" sectors to fast storage.
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By the way, the advantages of clustering sectors should also be easy to understand.
First, clustering collapses the size of the data that the volume manager needs to understand - using 512 KiB clusters reduces the number of elements by a factor of 1024.
Second, clustering helps you find hot spots.
Consider if you read a 512 KiB region twice. Without clustering, you have 1024 clusters (clusters of one sector) with a read count of two. If you have 512 KiB clusters, though, you have one cluster with a read count of 2048. With clustering, nearby accesses can be more easily seen.