High school and college grading standards do tend to differ. Remember that most college students were 3.0-4.0 GPA students in high school, but they get spread across the 2.0-4.0 GPA range in college (some fall below 2.0 GPA and risk academic dismissal). So it is common for college students to have lower college GPA than high school GPA.
However, it may not be that common for a dual enrollment arrangement to assign different grades for your college and high school record, even though it could based on applying high school versus college grading standards. It may look a little odd to an admission reader, or pose a question if you have to recalculate a combined GPA including both your high school and college courses.