I was more concerned with the oversimplifying part. This comment is more than antiquate.
I mean... Main Theme and the Chocobo Theme are Uematsu composed tracks. Sure, he didn't arrange FFXV's, but he still composed the original motif and basic composition. I am pretty sure Suzuki is credited for Hellfire on composition and arrangement. But things like RAVUS AETERNIA (which I am so glad Suzuki arranged) use a lot of motifs in the game that are layered over each other. I do think people who compose these motifs deserve credit for it, but if an arranger adds their own compositions to a piece of music they should also be credited for composition of a track. This is why crediting composers and arrangers is so murky. It takes a group of people to make a piece of music and not just one individual these days.
So yes, Uematsu, Shimomura, and Suzuki should be credited as composers when their compositions and motifs are used. The problem only comes when people don't want to credit more than one individual.