It does make perfect sense that a larger body requires more nutrients, which naturally would mean either more servings or same number of larger servings of nutritious foods. The whole "serving size" idea is so incredibly vague and inaccurate to start with (and so variable around the world) that it really isn't a surprise that it needs to be varied based on body size, too.
It makes more sense to me to focus more on nutrients than on random "servings", and I really liked the idea I saw in an article some time ago that ignored the "servings" but recommended intake of at least 30 different plants (including grains, nuts / seeds, legumes / pulses, and vegetables and fruits) every week. The article suggested that this minimum variety was associated with a stronger and more diverse gut microbiome, lower antibiotic resistance, and perhaps (correlation, not causation!) better overall health. The idea appealed to me, and I found that following it allows me to ensure an average of over 112% of RDA of most vitamins and minerals - which means that I am getting in the higher nutrient levels required by my body size / activity / metabolism.
This approach has me including 20-25 different plants every day, and averaging 32-35 different plants over the course of a week --- and incidentally results in me having 10-13 "servings" (based on the UK idea of 80g of cooked or raw, or 30g of dehydrated / dried) of vegetables and fruits every day. For me, the focus on getting in a wide variety of nutrients takes precedence over focusing on just "servings" of vegetables and fruit, especially now when fresh stuff is all imported or very expensive greenhouse stuff. While I do enjoy and use frozen and canned (I preserve a lot of local / seasonal), it is easier and cheaper to get the same nutrients from other sources, too!
Sir Terry Pratchett: "Science is not about building a body of known 'facts'. It is a method for asking awkward questions and subjecting them to a reality-check, thus avoiding the human tendency to believe whatever makes us feel good."
When fruit/veggies are plentiful in many places, I don't know how people CAN'T eat them. I used to eat 14-15 full serves a day, and THAT is what I HAD to cut to drop my calories and increase protein and lean fats to enable me to lose weight. I now only eat around 10 full serves a day LOL!