https://victorysportsnews.com/articles/4441/original
Here is an interview with Keiichi Yano who is the music editor of Hanyu's Hope & Legacy as well as SEIMEI. The music editor is a very well known person in this sport in Japan. According to him, Joe Hisaishi doesn't like his multiple musics to be edited/combined into one piece since every music has its own concept. Thus the editor and team Hanyu had to try hard to get an exceptional permission from Hisaishi so that Hanyu can use two musics of Hisaishi's in his Hope & Legacy program. Prior to Hanyu's case, it was well known that Takahiko Kozuka couldn't get a permission to use Studio [Ghibli's] original source of the musics (composed by Hisaishi) and Kozuka had to re-record musics by himself when he skated to Fantasia for Nausicaa.
BTW, the interview with Keiichi Yano is a very interesting one talking about the history of music editions in this sport in Japan.
Here is another interview. It's with Joe Hisaishi and it's on JASRAC official site. He says he wants to respect Japanese law even when he works with people outside of Japan.
http://www.jasrac.or.jp/sakka/vol_21/inner3.html
ETA:
Article about Hisaishi's concept for Hope & Legacy (original music), it's on the lower half of the page.
https://hibikihajime.com/information/21798/