The appearance of Gil was something that shocked many. They were surprised that he would be able to walk through the air with such ease. But they were also surprised to see the runes that they could not replicate except within their paintings and murals.
The runes followed the designs of many elves carvings and paintings. Replicating the growth of multiple plants and animals. It was more easy to say that they were changing tattoos. But they were only active with the addition of manas from surrounding nature and not from within. This was why it was thought to be something incredible.
This was a literal and metaphorical sign that Gil had met with the essence of nature and understood more key points about the flow of nature as a whole. That he had not only accepted it within himself but also been accepted by it.