You get the feeling some project manager at the RCD factory was not keen to pay for a new set of plastic mould tools to be cut, so the cheap thing was done and the sliders just withdrawn on the one they already had that was originally used for the RCD socket version.
Or if its really cheap then made with the holes and filled in afterwards. I imagine on the back you can see the filling sprues . If you are really lucky the distortion of the front from flat will reveal the section thickness as well.
Good mould makers charge 20-50k per mould to compensate for those sort of errors for a good reason.
It gets better, the SFCU is supplied from the old immersion heater wall switch, the customers called a stair lift engineer out after it stopped working only to be told it did not work because someone, possibly a grandchild, had turned the switch marked water off on the wall the other side of the airing cupboard.
Sometimes you look at things and just think "Why?".
