Inspiron 15 7590 keyboard not disabled during S3 sleep

The Inspiron 7590 comes with s2idle sleep enabled out of the box. In this mode, the keyboard is disabled when the lid is closed, preventing accidental resuming from a light squeeze. However, in standard S3 suspend mode ("deep" sleep), any key press will resume the laptop from suspend. This very easily becomes a cause of accidental wakes.

I prefer standard S3 sleep due to the significant power savings when suspended when compared to s2idle sleep.

I suspect this is a firmware bug, but I wonder if anyone has any ideas how to work around the issue?