Yesterday I created a new iOS build with Unity 2018.2.17f1 and I noticed my custom splash screen reverted to the default Unity splash screen. Creating a build with Unity 2018.2.16f1 gave me the desired results. I was wondering if anyone else has experienced this issue, and knows of a possible fix. My player settings are unchanged!
Was skimming through my questions and I just want to point out that this was caused because I was using the local cache server. Disabling this and deleting my cache resolved this.