Accepting that awareness is universal does not mean that all experience is common. Awareness sits at the core of a conscious experience, but it is an experience which is limited, bound, finite. The experience exists only so-far as the mind-body system.
If each mind is a walled garden, then within each garden there is an (identical) awareness at the centre, observing things which come and go within the garden. It is the mind-body system which defines the extent of the garden - it is the wall.
Although the observers are identical, the gardens are unique. Even the same event observed by multiple people is separate - because the experience of observation is an inner one.