My take on this.

Tbh I think the story would've been more interesting and just like the author said more 'attractive' if all three of the characters ended up together, I just couldn't help but miss the cuteness and brattiness that Sungyool added to the relationship, with him gone it felt like the dynamics became a bit flat and way too calm, Sungyool and Heejae bickering and fighting for Jisuh's attention was so intriguing to watch and somehow gave me butterflies, Also Jisuh depended a lot on Sungyool whenever things got too much for him (During sex, he was holding on to him a lot of times while Heejae was being the tough dom that he is) and Sungyool was consistently showering him with affection, plus Jisuh was really weak for Sungyool's cuteness, I couldn't help but feel like that dependence and soft spot he had for him would eventually turn into love. and of course Heejae and Sungyool already had a history together...so, TO ME it would've been more amazing and natural if the 3 of them ended together instead of cutting off Sungyool just like that. But with that being said I still enjoyed the story till the End :).