Personally, this phenomenon is similar to that potatoes in winter are sweeter than potatoes in autumn, which may be because the northern light frog lives in the extremely cold Arctic and forms a mechanism of polysaccharide decomposition in the body, making it slightly sweet!
The mechanism of polysaccharide decomposition, for example, people often feel sweet in their mouths after strenuous exercise (or in very cold environment), which is due to the decomposition of glycogen in the liver (muscle) in the body! Only in the human body, this mechanism does not always exist.
The above is only for personal understanding and reference only!