Pulling up an interface utilization graph, it defaults to 1 day resolution. Using the graph edit feature changing the resolution to 1 hour, then applying the settings results in the same 1 day resolution when the graph comes back up. Double checking again, the setting are set for hourly, but again the graph is daily.
Over 90 days
Release : 3.7
Component : IM Reporting / Admin / Configuration
With the role right "Run Dashboards At Higher Resolution" the maximum number of days you can a report with hourly samples is 90 days and the report you provided was over 90 days so it defaulted to daily samples.