I have seen it. Didn't work too well.
Same here. The ones I have seen were the ones I had service calls on for them not pumping out the water.
The splices make bottle necks in the drain hose and a nice little edge were the splice is for things to catch on.
Why do they want them longer? Let me guess...
They bought a portable dishwasher, but they don't want to wheel it over in front of the sink to hook it up every time they want to run it.
They want to leave it at the end of the counter and run longer hoses over to the sink.
I'm I right?
If that is the case they could just as well have the drain and water plumbed to it like a built in dishwasher. I have done that for people before.