Difference between Request Course and Enroll Course if both appeared to the learner

Dears,

Any Idea regarding the issue below.

The customer requires approval cycle for courses so we have set the enrollment setting for learners to requested while the offer is active then we have noticed that there are two ways to enroll either by clicking on request button or enroll button and if you select first the request button and after getting the course approved, you have to click enroll and waiting again the enrollment to be approved. Any Advise