You are absolutely correct,
The chicks will congregate in the heat when they need the warmth and disperse from the heat source when they want to be cooler. The first week of brooding has a target temp of 95, then each successive week, the temp goes down by 5-degrees. i.e. 90,85,80 by the 4th week, chicks begin to feather well and can usually be in the ambient temperature.
If chicks press against the area of the brooder farthest from the heat source, they may be too hot. You can lower the temperature by raising the distance of your heat lamp from the floor of the brooder.
It's just 48 hours since the first of my 6 hatched on Friday morning. With our TX heat, I'm beginning to wonder how large an area I will need to have them be able to be cool enough.