When you hold a spyglass and look at an entity and look a bit to the side then you start to see the shadow of that mob even when you are not looking at it

When you get a spyglass out and look at an entity (dropped items, mobs ) and you look over to the side you still see the shadow of that mob or dropped item (does not include armor stands as far as I know)

Steps to recreate 

1. Log onto a world on Minecraft on the Nintendo Switch.
2. Go into the creative inventory and grab a spyglass. 
3. Use the spyglass to look at a mob or dropped block. 
4. Look to any side and in the black outlines around the spyglass you will see that entities shadow and/or legs.