I don't know about the X13, but a lot of ThinkPads you can control the LEDs with some settings; /sys/class/leds/tpacpi::power/brightness on Linux (also some other knobs/LEDs in there).
Thus far this has worked on every ThinkPad I've had; but again, I don't know if it will work on your X13 (or how to do it from Windows or other systems), but something to look at if you haven't already.
Looking at the Linux source "tpacpi::power" is in the "TPACPI_SAFE_LEDS" list; the setting mentioned in that thread only protects things like "tpacpi::dock_active", "tpacpi::dock_status1", etc.
I checked, and my kernel doesn't have that option, and I can change it just fine ("echo 0 >/sys/class/leds/tpacpi::power/brightness", as root of course).
Thus far this has worked on every ThinkPad I've had; but again, I don't know if it will work on your X13 (or how to do it from Windows or other systems), but something to look at if you haven't already.