@zoe_kim - Your understanding is correct. Attribution IQ is unintuitive in nature, especially when used with Marketing Channels. With Attribution IQ, the credit for any success event will only be given to the channel that had an instance during the reporting window. If a channel persisted through the reporting window and it didn't have an instance, the credit will be given to "None". The dimension "Marketing Channel" is used with Attribution IQ.
Just for example -
A visitor came through Natural Search on May 1, and later came through a Direct channel on June 1 (no Marketing Channel instance was set as Direct ideally doesn't overwrite other channels) and purchased a product -- in this case, the Order will be credited to "None" on viewing the report for June 1 and not Natural Search even though Natural Search persisted through the June 1st hit.
This logic isn't applicable when using the "Last Touch Channel" dimension.