Not to put words in @ElvenArcher’s mouth, but I believe the point (and use of the word ‘stacking’ in the odds) is two-fold:
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The first interpretation of ‘stacking’ is that the odds do not remember a streak that has gone before (the Gambler’s fallacy). So having had a long streak of no luck for 5* will not make you any more likely to get a 5* next pull.
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The 2nd interpretation is in context of posts that @Blair and I have previously posted where we propose the idea of artificially stacking the odds after an abnormally long streak of no luck and/or a significant investment in gems. (Alternatively my idea of Shards kindly linked by @Kerridoc earlier in this thread),
@ElvenArcher can comment if I too got the wrong end of the stick. 
I think the point is a good one albeit not as clearly articulated as everyone would like. 