With the greatest of respect four people do not create a consensus - even in the relatively closed world of Discuss.
While no one would disagree that this is a mess and needs fixing, I happen to agree - and always have - with @Herman’s comment above:
Agree, the current definitions are confusing. The problem though is i.m.o. not the description, but the naming of the code. Post-completion suggests that this status comes after the completion status. This is not true though. The 'post-completion’ status comes before the completion status.
In other words, rightly or wrongly, code 4 (“Physical activity is complete or the final disbursement has been made, but the activity remains open pending financial sign off or M&E”) was defined to come before code 3.
To change the logical order in the meaning of the codes is a breaking change. This may well be a pedantic judgement and the bug fix may well be a pragmatic solution, but messing with standards is a slippery slope …