I recently went through the install process based on this guide and here is what I found:
Booting into the stock rom by accident after installing the /e/ recovery wipes the /e/ recovery and replaces it with the default Xiaomi recovery. It would have been helpful to have a warning about that in the guide.
The guide suggests powering off after flashing the /e/ recovery from Fastboot, then booting into /e/ recovery (Point 6 of the "Installing a custom recovery using fastboot" section).
However, attempting to power off by pressing the Power button for 15 seconds while in Fastboot would actually consistently boot straight into MIUI on my device, thus overwriting /e/ recovery, leaving me wondering why I was always greeted by the MIUI recovery again and again.
The solution I found is this: Instead of trying to power off by long pressing the Power button, hold Power + Volume Up while in Fastboot to boot directly into /e/ recovery.