The IRS no longer processes returns in first in first out batches. They are processed individually so returns sent in at the same time will not necessarily process together.
The IRS states that 9 of 10 returns will process in 21 days or less. However considering that the IRS processes more than 140 million returns that means 14 million will be delayed for more than 21 days.
Think of the IRS process as a long pipe line. Some returns will be rejected before being allowed into the pipe and the rest will be accepted. Then once accepted into the pipeline many will process directly through without any delays and some will not. Some returns will be siphoned off for further review of some kind. The basis of what triggers these reviews is a well guarded secret but some are just picked randomly every year.
If the person who gets an ID call and that was the last step in their process then the refund is released and that is just the way it is ... nothing you can do about how long it takes for the IRS to process your return and how many reviews your return goes thru or how long it takes a human to look at the return as the IRS is very understaffed ... and you can thank Congress for under funding the IRS.
