In reply to Durkules:
I would guess that there is a risk assessment / operating procedures in place that says that all groups must be supervised by an approved staff member. And the staff will be aware of that.
You need to find out who actually 'manages' the wall and put a case to them with regard to individual use. Use the standard 'sign-in' form used by most commercial walls as a means of reassuring them that it isn't unknown for individuals to use walls
Many walls allow unsupervised use but, at the end of the day, its their wall - its their rules.