XWidget supports seconds like Xanimateclock.
Even because all the animated clocks are created with XWidget Designer.
The answer is purely practical. Because if XWidget had the same animated clock widgets, there will be no reason to have Xanimateclock app. We wanted a separate app for animated clocks only and give a reason to the users to try both.
We don't want to have clone apps in our collection and force the users to buy both without a real reason. This will be unfair and dishonest.

At the end don't forget that since XWidget supports seconds for digital and analog clocks, users can always create their own animated clocks!