No, only statically linked programs are NOT affected by the change in Glibc.
If you wrote a program which accidentally did a memcpy when it should have been memmove, and (due to implementation details in memcpy) this worked just fine for years, you might not find the bug. A user who installed your application, which worked fine for years, and never upgraded the app but upgraded glibc, will suddenly find that your app is broken. Maybe you found and fixed the bug in a later version of the app. Maybe not. The point is that the user, who knows nothing about memcpy, now has a broken app. And the app might only break under certain conditions. And it might result in any kind of error: crash, corrupted data, silent corruption of data, audio or video glitches, who knows. These users are being punished so that someone else potentially might have a slightly faster memcpy.