Central ventilation system / also in the basement room?

Sorry, but in my eyes that is not correct. Do you have any evidence for that? What exactly is supposed to happen there?

Neither is an unheated basement room cold (it does not fall below 16 degrees in the coldest winter), nor does the controlled residential ventilation blow in moist air. Especially not when it is extracting. The temperature through the controlled residential ventilation will not change significantly either.

I don't see a problem there, on the contrary.

Moreover, he said that in an unheated room, moisture could form due to the supply of warm air. This point actually seems logical to me; moisture from the warm supply air condenses on the cold surfaces.

We currently have this situation in the (rented) house, and the exact opposite effect occurs. House (built 2009) with underfloor heating/gas, basement unheated, thermally not separated and no separating door, controlled residential ventilation exhaust air in the basement. If the controlled residential ventilation is turned off for several days, the humidity in the basement rises. We once switched off the controlled residential ventilation during vacation. After 14 days, the whole house smelled musty/damp starting from the basement. Two days after turning the controlled residential ventilation back on, everything was fine.

We only heated the hallway in the basement. Controlled residential ventilation only in the utility room. In hindsight, it would also be good to have controlled residential ventilation in the remaining rooms (hobby supply air, basement 1+2 exhaust air).

Do you have evidence for that?

Should I now give you the ISBN of my physics textbook?

Example:

21°C warm air with a relative humidity of 50% contains about 9g of water/m³ and has a dew point of just over 10°C.
That means as soon as this air cools below 10°C, water condenses out until the dew point is exceeded again. This usually does not happen in the living area because all surfaces are warmer than 10°C.

An unheated basement has an air temperature of 10°C according to the standard (especially if it is thermally separated from the living space above by insulation). Now if the 21°C warm room air from above cools down to 10°C, the relative humidity increases to 97.5% and the dew point drops to just over 9°C. In a 10°C cold basement, there are now almost everywhere surfaces that are colder than these 9°C and it gets wet there afterwards.

Basement unheated, not thermally separated and no separating door either

In this case, the basement is not "unheated."
Of course, you can solve it that way, but I believe most people do not want to simply blow their expensively heated air out of the house via the basement. And as soon as the basement has been thermally separated and a door prevents uncontrolled mixing with the living air, what happens in the example for no longer occurs.

I did not build the house

Yes, thanks for the example, but I already knew that myself. In fact, this no longer applies to any new building and is therefore purely theoretical.

As you can read here, in practice it is much better to connect all rooms. And if it costs 3 euros a year, the reduced risk of mold would be worth it to me!

Your initial post is wrong and unfortunately does not help the OP.