DQ for teeing off early?

Decision 6-3a/5 quoted by Region3, corroborates what is already in the words of Rule 6-3a. Nowhere does the Rule or the penalty statement mention starting late. You must start at the time established by the Committee; if you don't, you have a loss of hole or 2 stroke penalty if within five minute of that time (before or after is implicit). More than 5 minutes away (again either before or after is implicit) and you are disqualified. Starting before the designated time is just the same as starting after it: neither is at the time.

You mention a few minutes. As you will see from the Decision, it is necessary to establish by how much time each player is away from the correct time. Someone might have been lucky and teed off on time.