Line seperator in UITableView not displayed when running on Mac catalyst with option “Optimize Interface for Mac”

I have a problem with simple UITableView(Controller) with Style = plain and Seperator = default (all settings are default in the storyboard):

As soon as I select "Optimize Interface for Mac" in the target General Tab (Deployment Info), the separators are not displayed anymore when the App is running under Mac catalyst (Big Sur 11.2).

Any Ideas how to get the seperators back? Is this a bug or a feature?

Line seperator in UITableView not displayed when running on Mac catalyst with option “Optimize Interface for Mac”
 
 
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