tvOS / Xcode 12 Expected a type "UISplitViewControllerStyle"

I have a universal iOS / tvOS app with a mixed Obj-C/C++ and Swift codebase. The UI for the iOS & tvOS apps is mostly separate, save for a few views here & there.

Using the Xcode 12 betas (currently on beta 6), I am getting an error building the tvOS app in every Obj-C class that includes my Project-Swift.h header:

Code Block 
Parse Issue
   Expected a type
        Project-Swift.h
            (dozens of *.m and *.h files)

This is the section of the Project-Swift.h header that is generating the error:

Code Block 
SWIFT_CLASS("_TtC4Apex27SiteListSplitViewController")
@interface SiteListSplitViewController : UISplitViewController <PCOSiteConnectionStatusChanged>
- (void)viewDidLoad;
- (void)viewDidAppear:(BOOL)animated;
@property (nonatomic) CGFloat preferredPrimaryColumnWidthFraction;
- (nullable instancetype)initWithCoder:(NSCoder * _Nonnull)coder OBJC_DESIGNATED_INITIALIZER;
- (nonnull instancetype)initWithNibName:(NSString * _Nullable)nibNameOrNil bundle:(NSBundle * _Nullable)nibBundleOrNil OBJC_DESIGNATED_INITIALIZER;
=== // Error is on "UISplitViewControllerStyle" ===
- (nonnull instancetype)initWithStyle:(UISplitViewControllerStyle)style OBJC_DESIGNATED_INITIALIZER SWIFT_AVAILABILITY(tvos,introduced=14.0);
@end

In the iOS app I use an Obj-C UISplitViewController subclass, which builds just fine. In the tvOS app I use a Swift UISplitViewController subclass.

There is nothing in the UISplitViewController swift class that should be exposed to Obj-C. I'm assuming it's being added to the header because it's a UISplitViewController subclass though.

I know tvOS 14 defines single and double column split views now, but even if I try to go into the story board and update the style from Undefined to anything else, I still get the error. I've also tried changing the deployment target to 14.0, but that didn't change anything either.

If I build this project with Xcode 11, the offending line in my -Swift.h file (- (nonnull instancetype)initWithStyle:(UISplitViewControllerStyle)style OBJC_DESIGNATED_INITIALIZER SWIFT_AVAILABILITY(tvos,introduced=14.0);)
doesn't exist.

Again, I'm assuming it has something to do with the new UISplitViewController column styles in tvOS 14, but I cannot figure out what I'm supposed to do to get it to work, nor why my iOS project doesn't have this problem.