What is the difference in adding one Document in a field vs multiple Documents?

If the Training material closure scheme is set to Linear, by adding Documents to a Training as in method 1 you ensure that Trainees will read the Documents in the exact order you have defined.

By adding multiple documents in the same Document field, method 2, and using a linear closure scheme, users will still have to read the Documents in the required order but within each section they can read them in any order.

If the the closure scheme is set to random the documents can be marked as read & understood in any order.