System Information
Operating system: Linux-5.0.0-37-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.50

Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: rB26bd5ebd42e3

Short description of error
Blender can't add a movie, that is from a nested directory, in the Add -> Movie menu option of the Sequencer, until you have first added a movie from a recursive directory using the blender File Browser -- that is viewable by default in the video editing template.

Exact steps for others to reproduce the error

1. Open a new Video Editing Template
2. Go to the Sequencer and Add -> Movie from the sequencer menu
3. In the new import browser window, navigate to a folder that has subfolders with video files. (We are testing recursion here.)
4. Set the Display Mode (Dropdown) option to "recursions: One level" -- you can try more levels too, but 1 is enough to cause the problem.
5. Find a video file that is 1 level down (in a subfolder) and try to add it. You will get an error. (Report: Error: Could not be loaded)
6. Now, go to the File Browser editor, that is part of the Video Editing template.
7. Go to the same directory and set recursions: One level.
8. Drag and drop the same recursive file into the sequencer -- it will work.
9. Now, go back to the Sequencer Add-> Movie option, and now you will be able to add all recursive videos without a problem.

To sum up, it appears that there is a mystery recursion setting that is turned on only when you import a video from a recursive directory using the File Browser Editor in the Video Editing Template. After it is turned on, importing recursive files works fine.