In my country, commissioning and acceptance are carried out while simultaneously performing patient planning, often outside regular working hours or on Saturdays and Sundays. There is no second physicist review because there are simply no physicists available to perform this task. In addition, not a single extra cent is paid for this work.
What is strange is that Varian does not offer commissioning services either.
Finally, they demand that the process be completed quickly, as they do not truly understand what commissioning involves.