Discrepancy between terrain and gameobject size/scale

I have only recently started paying attention to terrain, and noticed that the scale between the terrains and the gameobjects are different. Terrain size as far as I can read is in meters, so a 2000m x 2000m terrain should be the same size as a 2000 unit by 2000 unit plane, seeing that 1 Unity unit = 1m. This does not appear to be the case.
I am using standard Unity 2019.3.f01 (empty project, no assets or packages added), and attached two images below to show what is happening. The white square is the plane (2000 x 2000), and the small blue/grey square in the middle is the 2000m x 2000m terrain. Is anyone else having this issue?

 

Someone on Reddit was kind enough to explain what is happening. For some reason a Unity Plane is a 10 x 10 unit, and with a Plane specifically 1 unit is 10m. Comparing this to a normal cube gameobject, a 10 x 10 x 10 cube will have a the same footprint as a 1 x 1 plane.
This to me is a bad ui design, and a recipe for disaster as there is no indication in the Unity editor that the plane is handled differently. Be careful when setting up a new scene and using planes to set up your scene size and locations.