Controlled residential ventilation and still open windows at night

I'm not saying it's impossible. Only, instead of turning the ventilation up and down, in my opinion there's nothing against opening the window for 5 minutes...

No, there's nothing wrong with that either - I just find it unpleasant in winter when you do it that way.

As I said, in case of emergency press the button and the ventilation goes to a high level for a predefined time and then back to automatic mode.

I was at my brother-in-law's yesterday. He has an LWZ303.
As far as I know, the device works with a constant volume flow.

He says the device has a "summer mode." It detects when a certain outside temperature is exceeded during the day and when a certain temperature is then fallen below at night/evening. In that case, the device automatically switches to supply air off / low and exhaust air possibly stronger.
You now have to manually open windows to let in cool air.

How exactly it works 100% / in detail I don't know, it may also be that I didn't quite reproduce something correctly.
What I want to say with this, however, is that such functions may exist, which probably operate differently from device to device.
A bypass could achieve something similar.
But this function supports my assumption that opening windows is not harmful to the devices.

The ventilation system reduces the supply air so that no warm air is sucked in, at the same time you are supposed to open the windows so that "KÜHLE" air can come in??? How exactly is that supposed to work? If it is warm outside, no cool air will come in through the windows either...

Uppercase letters and question marks usually do not help in interpersonal communication.

I wrote "[...] and the dropping below a certain temperature then at night/ in the evening."

So it is about cool air. And it comes directly through the window into my bedroom instead of through the duct system.
Admittedly, whether this really has an advantage over the bypass I cannot say.
In any case, there is this option and he uses it very often and is satisfied with it.

As I said, I only wanted to express that there are functions that support/ provide for opening a window. This again refers to the core topic of this thread.
I did not want to discuss sense and nonsense. Although the people from Stiebel Eltron probably had a reason for it, even if I do not fully understand it myself yet.

That is not meant in a bad way but only as an emphasis
To me, it sounded as if cool air would then flow in through the windows during the day.
Sorry if that was misunderstood...