Is it based on the average American height(175cm) and weight?(85+kg) or perhaps it’s that height but below 25bmi?
The Recommended Dietary Allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular gender and life stage group (life stage considers age and, when applicable, pregnancy or lactation).
The reference heights and weights come from NHANES (National Health and Nutrition Examination Survey), which is a nationwide survey done in the US. They take the median weight from each gender and life stage group (and then calculate height based on median BMI for each gender and life stage group). You can see the reference heights and weights in Table 1-1 here: https://www.ncbi.nlm.nih.gov/books/NBK222321/