I do think the backlog in each state has an impact upon the lag in approval.
I also think the decisions, which are based upon the evaluations by and recommendations of the state's "Disability Determination" offices also determines what happens to each claim. If these disability "specialists" feel a claimant's condition is severe, they will very quickly approve the claim. Any condition not considered "severe"is open to "interpretation," which can mean having to go through a hearing , etc.

Best wishes to anyone involved in the application/appeals process.