Dual fan variants: advantages and disadvantages

I have never actually seen that in practice

Because they are also unnecessary oddities. There is no market for that.

Basically, the pipe in the middle is divided. (At least that's how I understood it). On one side there is a small fan and on the other side another one. They run almost counter-rotating, one blows air in, the other out.
According to my understanding, this should also be less efficient than a large fan that reverses after a certain time. But there must be some reason for it, hence my question. Maybe it saves having a second fan at the other end of the room?
There is, for example, the ego from Lunos, but I have also seen it from other manufacturers.

Is there, for example, the ego from Lunos,

which is intended as a functional fan for bathroom and kitchen.

Maybe you can save one fan at the other end of the room?

No. Why? The Lunos ego also works in reverse. It is also said to be terribly loud and inefficient due to the small fans (these are the experiences found online - also here in the forum).

Exactly for that reason, this concept apparently has many disadvantages, so why does it exist then?

why does it then exist?

To sell something really great with a unique selling point...

You can also buy quadruple-glazed windows, which have a slight thermal insulation advantage but come with a lot of disadvantages. They also sell well and expensively. Or you can buy super sports cars - advantages of this type of car? Or 8k TVs. And so on.