I'm confused about the ESD folder. If I install Windows 10 with the Media Creation Tool, an ESD folder is created. I understand that this folder should not be deleted if you plan to use the Recovery feature as it includes the files need to reinstall Windows.

If I reinstall Windows by mounting an ISO, run "setup.exe" and select "Keep nothing", however, no ESD folder is created, but I can still use the Recovery feature. The following blog article about how Windows 10 achieves its compact footprint explains why this works:

How Windows 10 achieves its compact footprint | Windows Experience Blog

If Windows 10 is able to run the Recovery feature using the runtime system files stored in C:\Windows\WinSxS, why do I need to keep the ESD folder if an installation was done with the MCT?