The Natural Philosopher wrote:

Blimey.

Imagine what AFDDs are going to be like, a DSP to discriminate between
harmless sparks and fiery sparks?

I'll concedeÂ* that. They have devloped since my time...BUT if
you look at the circuit diagram later in that video, you will see than
no earth is involved.

Yes, the reference circuit for the chip shows it has a "substrate ground"

http://eng.fmsh.com/AjaxFile/DownLoadFile.aspx?FilePath=/UpLoadFile/20140904/VG54123_ds_eng.pdf&fileExt=file

but no PE or FE earth connection, makes you wonder if MK have added
something extra on the PCB for lost-neutral detection?

The only possible thing it *might* do is nothing
to do with RCD detection per se,Â* but it MIGHT detect voltage on the
neutral with respect to earth.

Not something that bothers me at all.