In another forum this article regarding the audibility of group delay was shared by a member and I thought I'd re-post it here as it may interest some:
https://drive.google.com/open?id=1J66XIE-mgaDOWWarOjuDmhYKfC6kKXPw&fbclid=IwAR1pOpV9MwuqkUjfFOv4joweTbHKr_Tat_yloKmUl6X9RH4wYQh0ZuMPQDE