The Grandmaster's alchemy technique looked simple as Saleen was able to understand every action and every alchemy principle, but the materials he used were things that Saleen would never be able to get his hands on.
Without those materials, one would never be able to refine equipment of the same grade. In other words, the Grandmaster was not hiding any of his techniques from Saleen, but the latter would still not be able to replicate what the former did.
Saleen knew that the Grandmaster was doing that on purpose, but the former pretended to be unaware. The difference in their grades was too huge. For the Grandmaster to pass on his knowledge to Saleen, or to make sure that Saleen would not be able to learn a single thing, both were equally simple to Grandmaster.
