really lovely but this author has a major case of same face syndrome
Eh, disagree. A truly major case of same face syndrome would be the Fubuki class of Kancolle.
Anw, at the last page you can see that when the author pays attention to details, the characters' faces are different. They probably just got lazy and didn't want to detailed every pages of a 78-page oneshot, which is fair.
Also, as someone who can't really see and remember people's faces (both real and fictional), I didn't even realize that until you pointed out.