When "Minimize to System Tray" is checked, and the option is confirmed with "OK", VoiceAttack will create a system tray icon and remove itself from the taskbar.
If the window is minimized and restored, the taskbar entry will not reappear.
However, when VoiceAttack subsequently starts with the option enabled, the taskbar entry will be present whenever the window is(even after minimizing and restoring).
Opening the options and clicking "OK" while the "Minimize to System Tray" option is still checked will again remove the "VoiceAttack" entry from the taskbar.
I observed this in v1.6.8(the oldest I tested), v1.6.9 and v1.7, on my physical machine, a Windows 7 VM, and a Windows 10 VM.
EDIT: Fixed in v1.7.0.2