It hasn't been true since 1.3 when all of the custom sets were expanded to include additional pieces.
As far as I can tell there are only three "full" i.e. seven piece sets for each of the different weights of armour and these sets are all the "neutral" ones. Coincidentally I outline the schematics missing from each of the sets
at the weekend. Please note however that I've only looked at synthweaving so far.