Good question, Dan !!
Livescope in Perspective Mode shows shadows, so it may just be the shadows are there when using forward facing mode, but the bottom glare swallows up those shadows or the shadows disappear in the distance.
Then again it could be the design of the software to show the on-screen images differently. Sidescan takes images as the boat moves, while Livescope takes images continuously, whether or not the boat is moving. If the boat isn't moving or is moving very slowly, Sidescan images are almost static or collectively placed on top of each other and basically smeared across the screen. Livescope simply continues to show a "live" screen presentation, capturing movement & static images even while the boat isn't moving.
It's kinda like : Sidescan = camera pics taken in rapid succession & Livescope = video camera images.