It is Boeing procedure to reset the IRS's.
I flew for airlines that did full align at crew changes and fast align on same crew turn-rounds. Boeing designed the fats align feature, so we used it. I then flew for an EU airline that full aligned every sector. After a few years there was a Boeing audit and the TC asked why we did that. It changed to the former procedure at Boeing's advice. So, there are 2 methods to reset an IRS.