Changing person name format not working on username and initials

Summary:
Hi Experts,

We have amended the name format for all the global name formats and the UK one to add preferred name.  I have also set the profile HR_LOCAL_OR_GLOBAL_NAME_FORMAT to global format. so far names are appearing as I would expect in most areas but there are a couple of areas that I have identified where it does not show as I would expect
1.  A persons user name and brings back what it was at the time rather than what it is now.
2.  The bpm worklist shows for some people the revised person name and for some it shows old name.  Does this depend on how we have submitted the change?