OK, this is my point of view on WSM.
The mail arrives in trays and will be in the exact order of your frame, so as you pull a bundle out, it will run in order according to your frame.
Q: Will it save me time ?
A: NO,
unless you are new, an experienced postie will know his/her frame very well and will not chuck out WSM any quicker than un-sequenced mail.
Q: Why are they introducing WSM ?
A: WSM is there to remove the skill factor an experienced postie has. Using WSM means they can now bring in any old Tom Dick or Harry off the street and he or she will be able to chuck that round off just as quick as an experienced postie can.
So what WSM has done is, remove the learning period from a new starter, one of the hardest parts of a posties job is to learn the frame, using WSM there is no learning ! and so RM benefit.
Don't be fooled by what your DOM tells you about WSM, it is utter crap.
Is WSM good ?
For Royal Mail yes, for the postie
NO