Article - Justifying your own background

Right then, here goes nothing. I'm going to try and explain a recent brainwave I've had, and to some it's not going to sound special, and to others it will, and the rest will just get confused by quite likely third option; "I won't succeed in wording it and so it'll confuse you". Anyhoo, here goes:

Background is key to this little hobby of ours, for some it's far more important that it is for others. This is a slightly over the top example.
For example; Person A states his Ultramarines represent the 3rd company of the Chapter, and they are in such and such a sector on such and such a planet on such and such a date fighting this enemy, whilst Person B then reads it and states "No! That's impossible, they are already in such and such an area fighting a different enemy on this date in the background, it's in the codex on page ....".
Well, this is going to be a complete no-brainer I expect, but here's my rather long-winded explanation for how both can be justified in terms of fluff:
You split, and create strains of the in-game world, I'm using 40k in this example as it's quickest to explain and is most likely to be well known, although I had this brainwave when I was writing some fiction for the Kingdom of Britannia force for the upcoming Dystopian Legions game (shameless advertisement there I know). E.g. the in-game world as it stands in it's original form we'll call strain 1, if you stick to it as far as novels and official codices go , it carries on being strain 1. In Person A's background his force is also the same as a force from the official background, sticking with the original example of 3rd Company Ultramarines, well, if in Strain 1 they are in a different planet to where Person A wants, then he can justify this by making Strain 2, it uses all the same places and forces as the official background, but the force isn't in the same place or potentially made up of the same characters or units as the "official" background, this creates a new Strain of background, Strain 2. This can carry on, with more and more strains, and here's a diagram showing the same principle (hopefully in an easier to comprehend way - trying to explain this went into some grey floaty universe on Friday night when I was trying to explain this to some of my friends at a local club):

So, we have a completely seperate in-background universe per person that seperates to fit their own interpretation of the in-game universe and how things work, what's in it and so forth.
This isn't saying steal a companies in-game universe for your own ends, it is merely allowing you to add to it whilst avoiding fluff-lawyers from attacking your ideas.
Hope this has made sense.
Till next time readers, when a picture-full update of this week gone and this week coming's painting progress will be posted (I've gone back to painting Romans for a little bit, as they look a bit sad clogging up the painting desk).....