With roof insulation, no attic

Acquaintances of mine have newly built. I was somewhat surprised today by the quite high ceiling on the top floor. Since it reaches up to the ridge beam, it is certainly about 5m there. On average, I would say 4m. After I asked whether there would still be an attic space, I was told that this would not be the case. The reason is that an attic collects too much moisture with a fully insulated roof, which would lead to moisture damage in that area. This apparently happens even when properly and sufficiently insulated, and vapor tightness to the outside is established, etc. It would only be possible if you insulate the attic as living space and provide ventilation in the attic. However, that naturally contradicts the external roof insulation. As an alternative, a suspended ceiling is apparently being considered. However, I now wonder what the difference is between a suspended ceiling and an attic. The suspended ceiling is not airtight but causes poor air circulation in the upper area, i.e., from the suspended ceiling to the ridge beam. So basically, it is the same situation as with an attic. Now I am naturally wondering how all the old buildings that have retrofitted or are retrofitting external roof insulation deal with this problem (like me, for example :)). I absolutely cannot imagine that in all old buildings where external roof insulation is installed, the attic is either removed or the attic is insulated as a thermal boundary and accordingly ventilated. That would make the external roof insulation uninteresting again. Therefore, I must have misunderstood something here, or something else is still unknown to me? By attic, I mean the “small” roof spaces with a room height of, say, 1-1.5m. Typically, you can only access the attic through a hatch. How is it with you?