I think Mleake assessed it correctly. The article says that SWAT officer's eye movements are consistent with a flash sight picture while rookies spent too much time re-verifying sight alignment. SWAT officers, who have more rounds downrange/experience, spend less time confirming their sight alignment and once aligned, shot the target instead of checking alignment yet again. Shocking findings.
How did they get to that level of confidence and speed? Probably with a lot of time spent verifying the sight alignment in training so that it was second nature.