Valid only for the Shelly Qubino Wave 1PM with the firmware version 10.13
In the mentioned firmware of the Shelly Wave 1PM it has been observed that the device is capable of reporting a maximum of 1W when in an ON state and without any connected load. This behaviour is attributed to the sensitivity of the device's measurement chip, which detects even subtle fluctuations in power, including incidental electrical background noise, leading to minor power variations.
The firmware update version 11.05 available for download at this link has resolved the issue.