.tscn's are not imported as .scn despite documentation stating otherwise

**Godot version:**
3.2.3

**OS/device including version:**
Windows 10

**Issue description:**
The Godot docs state that any .tscn is imported as .scn to save space and decrease load times. This only seems to be true for .escn.

**Steps to reproduce:**
I've tested this by exporting a project. Once with a comically large .tscn (thanks BakedLightmap) and again with a .scn counterpart. The one with the .tscn was larger than the one with the .scn. I've included that here. (You'll have to manually export it yourself as GitHub doesn't like files bigger than 10mb [preferably with export all])

**Minimal reproduction project:**
[BigScene.zip](https://github.com/godotengine/godot/files/5397063/BigScene.zip)