Every one of us have 'sensory settings' that tell us when a sound, sight, smell, taste, or other sensation is OK or the reverse i.e it is too much to handle. It differs from one individual to another.
Sensory 'overload' (SO) is one of the major reasons why people with autism can end up having meltdowns or unable to manage in what most of us would consider to be ordinary situations like going to the football match, or shopping (I think I have SO when shopping!) or the cinema (my lad has to wear ear defenders in the cinema to help him cope and so that we can get him to watch a film that he wants to see). SO usually leads to him feeling anxious and being overwhelmed by things as well as wanting to get away from the noise that's causing the discomfort.
Obviously if you go into the middle of the Kop with all the noise and human interaction it's going to be at a heightened sensory level than going into a less populated area of the ground (Bramall Lane Upper Tier for example which is where we once tried to take him before it got too my much for him), but even so there is no given that all will be alright on the day, with the crowds outside, the anxiety (and excitement) of going to a game all a contribution along with the situation itself inside the ground and who is sat next to you and the noise levels. Often it's just too much for people who suffer SO to cope in that environment.
So an an area to move to if things are getting too much (break out den) and a sensitivity seating area is a big step in the right direction for enabling someone with Autism to manage a football match situation. It makes attending a football game possible now for him, whereas before it was off the menu.