Xcode 13ß1, deploying to iOS 15, UIKit using Storyboards.

 

I have a tab bar controller which (for one of its tabs) contains a split view controller. The split view controller is configured in the storyboard as:

 

Style: Triple Column

Compact Wide: Use Separate View Controller - NO

Present Master With Gesture - YES

Display Mode: Two Columns Beside

Behavior: Tile

Primary Edge: Leading

 

I have triggered segues to the three (primary, secondary, and supplemental) view controllers set up in the storyboard.

 

The split view controller has a delegate which implements splitViewController(_: topColumnForCollapsingToProposedTopColumn:) to return .primary. Moreover, the split view controller's viewDidLoad() method reiterates the basic settings:

presentsWithGesture = true

preferredDisplayMode = .twoBesideSecondary

preferredSplitBehavior = .tile

 

With the Simulator set up to use an iPad in landscape mode, running the app shows ONLY the primary column. I do NOT get the "two columns beside" display mode.

 

Obviously I am missing something obvious, but I just can't see it. What am I missing and/or doing wrong?