If the time range exported had more than one size or reporting period (hourly, daily, weekly, etc) it would always take the data from the largest available period. i.e. if 20 days were exported, the complete weeks in the middle would be used and the daily periods before and after would be added in after.
Any time range requested will report only the data composed of the same periods as listed by the request. For example, requesting a time range from “current day -1” to “current day -29” will only report data from daily periods. This will not take data from any weekly periods that are available. This change may possibly mean that some amount of uniqueness will be lost, as any visit/visitor that occurred one in a week but caused traffic on several days could be duplicated in each day reported back by the rest interface.
Also, this change will keep the output from showing data from smaller time periods. To show hourly data, you would have to specify hours in your start and end periods. Selecting the daily ranges will not present the hourly breakdowns