It is possible James Gunn was aware of Doctor Strange In The Multiverse Of Madness would likely include Shuma-Gorath when he was preparing to write The Suicide Squad. Gunn will probably never fully forgive Disney for firing him over social media content some executives found distasteful, and it is possible he found a way to stick it to them a little bit by using Starro, a giant sentient starfish, in his upcoming DC movie.
Shuma-Gorath and Starro are not identical creatures, but they both are large, have a big eyeball in their center, and have tentacles. Visually, seeing Starro first is going to make Shuma-Gorath look a little derivative when he/it appears on screen eight months later.
