User blog comment:B214/Volume 22 spoilers/@comment-95.90.227.74-20161018202609/@comment-29963364-20161020065926

Actually, it would be more accurate to say that Issei is a clone of Great Red.

His body was made entirely of Great Red's flesh. Nothing else. This essentially makes Issei's new body a clone of Great Red.

Ophis used her power to bind Issei's soul to the new body.

So Issei is more like a "Mini-True Dragon" with "Dragon God" power.