This is currently a limitation which will be fixed with Version 1.5. In Version 1.5 you will be able to select if the shadow only applies to the mask or the whole layer including all borders.
I finally submitted Logoist 1.1 to the App Store 2 days ago. I hope that Apple will approve it in the next 1-2 weeks...
The Mac App Store is such a good marketplace for developers and the review process is a good thing wouldn't it be taking so long to accept or reject apps. The developer forum at apple is full of angry developers who are waiting 3 weeks or longer for their apps to be approved.
Logoist has been designed to be iOS compatible in the future. The code is separated as a "Core" and the Mac GUI. I have a test version already running on iOS but it is far from complete or usable. My best guess for an iOS version is spring next year or summer.
As I said, a beta version is many months away but if you are interested, drop me a quick message to info@avisnocturna.com and I will add you to the testers list!