Opportunity Trends Report differs from the results of Opportunity History Report

The Opportunity Trends Report works as below:

1. The Records can be based on the changes that can occur with the Stage, Amount, Probability, and Close Date fields.
2. The Historical and Actual (Current Data) fields will be available in the Report Builder Fields, despite the Field History Tracking’s influence.
3. We can track the Trend as per a Specific Date, Date Range, or All Time by using the same in the Date Field selected for the Display.
4. Post setup of Date Field, as 'As of Date' the actual values of the fields and the Historical Values as of the date of the last day of every month in the included Date Range can be reported on.

In case of more than a month in Date Range, this might look like same record showing multiple times. However, they are the different Trends for the same record as of every month, the appropriate history information as of the same date will be displayed in History fields.

Note:

Most importantly, this Report will still populate the records where Edit or Update had never happened.

Opportunity Trends can report on the data where essentially no impact of Field History Tracking is not involved and is completely different from 'History Tracking Report'.