Excellent question.
No deductions are available for judges to take on arm circle. Judges can evaluate the shape/dynamics/flight/landing ( I am speaking in general). An arm circle can be used for timing balance or direction assistance for an athlete. I have attended US National Performance Clinics and the clinicians have spoken to using the tactic and not using the tactic with advanced or elite gymnasts. I see it as a valuable movement in our developmental athletes. As usual it can be taken to an extreme - huge arm circles that hinder the forward movement that changes quickly to an up and over movement in the front HS vault. A novice athlete, aka L3's big prioirity is to get an accelerating run and a straight shape. Keep the high priorities in mind and the vault will improve.
Best to your athletes with their vaults, SBG -