Cored decks and hulls have enough advantages that they were and are used. Stiffness, weight, elimination of condensation. Cored decks and hulls can be stronger than non. Just as your bones have a mushy marrow - a hollow tube is stiffer and resists bending more than a solid one . . . of the same weight.
I would not pass or fail any design just because it used a balsa cored deck. Have it surveyed. Very possible some prior owner(s) corrected any problem areas or routine maintenance has allowed the balsa to remain stiff and dry without needing a correction.
Triton #1 is on the same lake as us and undergoing restoration. The deck fittings are being rebedded but, as far as I know, the original core is in place. I can check if you like.
Our Pearson 31-2 had some balsa deck issues that were corrected and it passed the survey I had done before buying her. Required digging out some balsa and replacing it with filled epoxy. Don't assume balsa is a disease.
Charlie P. P31-2 #80 CATNAP
To travel hopefully is a better thing than to arrive - R.L. Stevenson
I suspect that, if you should go to the end of the world, you would find somebody there going farther . . . - H.D. Thoreau