Putting SOP and AFM things to one side, what disturbs me is that the 737 Classic is one of the easiest aircraft to land and ought not to require any magic formula.
A while now since I have flown the variant but, as I recall, all one had to do was fly it down the slot, flare a few degrees (with a degree or two extra in a strong crosswind to allow for the bank angle), close the throttles, and sit it on the centreline for the rollout .. the quintessential pussycat.
More particularly, while I can see some logic in having a preset trim for, say, bugging out of a form aero problem (and, even then, I remember watching a recorded TP flight for the Blue Angels when they were investigating this for the F18, as I recall - a bit of roll/yaw coupling and away he went into a gyrating departure - the HUD video was interesting and the TP somewhat chastened as he had been caught out totally unawares) - any routine flying out of trim has to be a bad practice.
Trimming during the flare has to be a great way to set yourself up for interesting control loads during a late miss ... potentially, such a technique could compromise certification considerations for the missed approach.