I also suspect that the wasabi they claim is in the product is leaf only to give the green colour to the mix,
Namida® 100% Pure Wasabi Powder Review
This product contains only 100% Wasabia japonica rhizome. You won’t be able to get any better than this except for possibly high quality fresh wasabi.
Clearspring Wasabi Powder
A review of this product. Ingredient listing. Reviewers comment and recommendations. There is not a pleasant sweetish after-taste, but a feeling of relief when the taste finally does go.