Unfortunately we have to maintain two different versions of Strongbox on macOS (in addition to managing Freemium vs Pro). Please see the reasoning below.
What is Universal Strongbox?
Runs on both iOS and macOS using the same license. Anyone who previously had an iOS license now has a Universal license (which will also work on macOS).
What is Non-Universal Strongbox?
Runs only on macOS - a separate license is required to run on iOS. Anyone who purchased Strongbox on macOS before the release of Universal licensing has a "Non-Universal" license.
Is there any functional difference?
Zero. Absolutely None.
Both Universal and Non-Universal versions of Strongbox have the same identical feature set and update schedule and always will.
So why the need for Non-Universal?
The reason we have both is historical, Apple provides no way for us to migrate older non-universal users to a universal license.