We have performed some learning experience development projects where the customer assigned many SMEs and did not plan any means of arbitration when two SMEs had strongly held and mutually exclusive opinions to provide to us as change requests. This situation is difficult for both the customer stakeholders and the development team, and it slows throughput.
One of the extra benefits of iteration demos that include all the applicable SMEs as attendees and with the customer leadership representative invited is that the SMEs tend to more easily work out any differences. The customer leader hears the issues and directs an offline solution after the demo with a due date. Or perhaps the SMEs involved hear each other out and realize they are more aligned than originally thought. Or sometimes, the customer makes a decision about which input to accept and which to not implement. Whatever the means for getting there, the demo provides the visibility into the issue at a level of observation of all the relevant stakeholders. It get resolved by the customer much more quickly this way than with endless emailed arguments back and forth. This is especially true when the iteration demo has a fixed time box and all are aware of the limited time to cover the major issues during the demo and to see working courseware for the increment delivered.