Are you saying the very same data gave you a different result before you switched from date-time to date type, than you are getting after you switched back from date to date-time type?

See what you get if you remove the 'order by date' from your view, and made your date column a row grouper.

Also, I wonder, depending on the sequence of events with this report's design editing, relative to your changing data type on the backend, if in the metadata for the report it thinks the type is text for the date column versus date-time. Try removing the column from the report, saving it, then adding the column back.