ANSWER
According to Technical Guidance Notes on Nutrition Labelling and Nutrition Claims and Regulations on Nutrition Claim for Prepackaged Food Products, there are no specific approval required for inulin and oligofructose for the use of nutrition claims in Hong Kong and Taiwan.
References
Hong Kong Food and Environment Hygiene Department. (n. d). Technical Guidance Notes on Nutrition Labelling and Nutrition Claims.
Taiwan Food and Drug Administration. (2015). Regulations on Nutrition Claim for Prepackaged Food Products.