"ChangeVersionNumber" in OM Extension behaves differently when order is revised using UI vs REST

Summary:

"ChangeVersionNumber" attribute in OM Extension behaves differently when order revision is created from REST vs UI

Content (please ensure you mask any confidential information):

If we are revising an order using UI, "ChangeVersionNumber" of the draft is one plus the version of the Open Order.
And, if we are revising an order using REST, "ChangeVersionNumber" of the draft remain the same as version of the Open Order.
This is the behavior when we put the extension in "Save" or "Start of Submission Request" tabs.
When extension is put in "End of Submission Request" tab, "ChangeVersionNumber" attribute value is correct but we cannot make any changes here.