Currently the tuple reader will only resolve aggregate tables only if the column attribute is the only one set. Setting other column attributes like the ordinal and name will cause it to go back to the fact table.
Comment from code:
// determine if any collapsed levels contain more than one column, if
// so, the aggStar is not compatible.
// In the future, this feature could be improved by:
// 1. changing the sql generation to join the collapsed level to its
// dimension table(s) to select the additional columns.
// 2. Create members that are missing these values and populate the
// values at a later time.
// 3. extend agg tables to support additional level columns