The Journalism Professor

A journalism professor of mine once insisted that it was grammatically incorrect to use "over"   rather than     "more than."   However, according to   https://www.writersdigest.com   there is no grammatical rule which prohibits using "over" rather than  "more than."    For example I had thought it would be grammatically incorrect to say,  "I had  over $10.00.  Now I know  it does not matter.