I don't care about this behavior but I felt like I should post just so it's documented somewhere.
Steps to reproduce:
Set up channel display and PSD in 2 frames in the same workspace.
Turn on scroll lock.
Highlight PSD.
Use arrow keys to scroll up and down- the PSD scrolls one line at a time.
Highlight channel display.
Use arrow keys to scroll up and down- the channel display scrolls one line at a time.
Use [Shift] + [Page up] or [Shift] + [Page down] - the PSD will scroll one page at a time.
