Here is some background to the issue. I've been looking at it for the past two days and to my knowledge everything is properly configured. To make sure that we are on the same page with versions that are being used I am using the following:
I have UISplitView that was added to the storyboard at a later stage of the project. The project was started form Single View template. Normally the left part consist of a UITableView. When Xcode added it to my storyboard it also had a prototype cell setup. I've added the needed Identifiers and now the prototype cell is accessible in my code. I've implemented and binded the needed delegate and dataSource protocols and checked that their methods are actually being called and working. I've also added background colors to the prototype cell and the prototype label and I see a cell when there should be one but it does not have a label. So here is a list what I've checked:
So pretty much I am out of ideas right now. Can you please help me on revealing this mystery?
To answer my own question.
I've created an empty master detail project and saw that this is working there. This made me think that actually there is some kind of a bug in Xcode when you drag and drop an UISplitViewController to your storyboard. For some reason the storyboard is not properly configured. I have no idea what is not properly configured but there is definitely something that is wrong.
Because of the above observations I deleted the UISPlitViewController and used a plain UIViewController to recreate a similar setup that will also work for me. As a result I was able to adjust my already existing code to the new View and use it without logic changes. Which to me just indicates that this is an Xcode issue.
Thanks!