NO. When balso is used as a composite core material, it is used in the "end-grain" direction. So you would cross-cut let's say 100x100x6mm lengths of your balsa and then arrange them side-by-side into a core. Done this way it is stronger than high tech foams, but not water resistant if you get a skin puncture.
What you describe is certainly the classic definition of core material in a sandwich. the balsa is aligned to maximise its compressive and shear properties.
truth is, the flexural properties for balsa are so much better than most other core materials that the balsa is frequently aligned length-wise to minimise the need for additional reinforcement.
cross-grain compressive strengh is still exceptional.
one of tthe most popular construction methods is to fabricate "sandwich" skins using 1/8" balsa planks for the core. The sandwich is laminated top and bottom over a very light core such as 1# EPS.
Similar to composite sandwich construction in surfboards and windsurfers.
lots of ways to skin a balsa tree.