HB is creating raw utilities within the actual algorithm, but in the output report we also show you the normalized (zero-centered) utilities.
The default report which summarizes the utilities at the end of the run for you uses the zero-centered diffs normalization. If you average the individual-level results on ZC-diffs, you should see they match the aggregate report table.
When you move the .HBU file into a market simulator, the .HBU file contains the raw utilities. Raw utilities should be used within market simulations.
Zero-centered diffs are useful for viewing the average utilities and comparing individuals or groups on the utilities, due to the normalization.