The answers you give to the questions are based on the information given to you by your GP (and maybe other medical professionals). If you answer the qustions on the form honestly then problems will be picked up. I agree though that if you do have any condition that requires DVLA access to your records using your GP for the C1 medical might speed things up.Your own GP does, that' why I use them,DVLA frequently ask for the records from the GP of the applicant especially if there is some medical history/problem.
This is what very often causes delays.