I wish they would add small UPS inside (like super-capacitor or something like that) there to provide way for forced sleep when power is cut off. It's a neat small device which must be accompanied by huge bulky UPS for reliable operation. If someone didn't know, macOS ignores fsync, so without UPS your data is not safe. Not an issue for laptops, obviously, but issue for battery-less devices.
How does macOS guarantee no data loss when shutting down normally?
FWIW while fsync() on Linux does request that the drive flushes its hardware cache, it's up to the drive whether to actually honor this request, and many don't do so synchronously (but still report success). So unless you control the whole setup end-to-end - hardware and software both - you don't actually have the guarantees.