I checked it Mac and Windows.Then,It happend v2.2.5,MacOS only.
See a comparison image a following.

I prefer that thin padding style for it.
Best regards!
My test Enviroment is:
Wings3D 2.2.5 on MacOS 10.14.6
wxWidgets-3.1.3 doesn't support mouse events on bitmaps on MacOSX for unknown reason,
I have made an error report on that, so I have to use buttons to catch mouse clicks.
I see.
dgud,Thank you for feedback to wxWidgets's dev and keeping of the usability.