@ solomonwise
We have seen many instances of random charging for application of a particular day, whereby early morning apps have been charged after few days of afternoon apps.
With ur assumption, you are assuming that every app require similar time and every reviewer has same speed. Thus, they start with early morning apps and gradually more to later apps. I would rather assume that apps are allocated to different reviewers (or teams) based on NOC and they review it at their own speed and as per the requirement of the app. (Single applicant with 1 yr experience will take less time than a family of 4-5 person with PA having 6-7 yrs experience in 3-4 different companies). Also, one particular day may have concentration of specific NOC, which will lead to more time required for that team to clear the backlog compared to another team responsible for some other NOC.
Moreover, as per CIC and Ministrial instructions, FIFO is only for dates not for apps received within a day.