You are holding the buttons too long before the USB insertion. The Honor 90 Lite has a "Safe Boot" override. Ensure the USB cable is already connected to a power source (PC) before pressing Volume Down.

: If the phone boots directly into fastboot without you trying, a physical button might be stuck. Gently clean around the buttons or press them firmly several times to ensure they aren't jammed.

Leo learned that the Honor 90 Lite’s bootloader gets “confused” by residual power from a USB connection. To fix this:

How to Enter and Exit Fastboot Mode on the Honor Magic 7 Lite