I haven't read Vulkan lives and Massacre ,but admitedly they could have said something like that about Salamanders .
Lexicanum says something interesting.
Originally known as the XVIIIth Legion, the origins of what would become the Salamanders are largely shrouded in mystery. In order to protect the nascent Legions Astartes from both hostile action and espionage, the origins and deployments of several early Legion gene-seeds are further classified beyond usual protocol. These Legion groups were formed and established largely in separation from the rest, and it is generally thought to a very specific end. The XVIIIth Legion, along with the VIth Legion and XXth Legion, comprised this group of proto-legions. That this 'trefoil' of three proto-Legions was somehow veiled from the rest during their creation and establishment was something known only to a few. Deliberate effort was made to distance these three legions from the others. There are none save the Emperor and a handful of his aids who know what the exact purpose behind this policy was