It allows a control to be wall mounted without having to run a wire from there to the bidet...
There was a toilet in Japan I couldn't for the life of me work out how to flush, I spent ages in this bathroom checking for buttons here and there. Only after I had given up and walked away from the toiled did it flush.
That's been a constant refrain about IR auto-flushing toilets for about 30 years. They were invented in 1988.
From a security point of view, it sure makes for an interesting attack surface
You have to look out for backdooring though.
That's one penetration test that I would not want to participate in.