Standard SharePoint behavior for Approving a document.
When a document is “Approved”, SharePoint is setting the value of the columns:
[Modified] = CurrentDateTime
[Modified By] = The account that does the Approval
When Versioning is enabled then the approval of a document always increments the version number to next major version.
Fusion implantation and enhancements.
When versioning is enabled, values in the columns [Modified] & [Modified By] are preserved and does not change.