Yet every time you ever see an interview with BL authors over the series they always say how they have frequent meets to avoid any continuity errors
Makes you wonder what they actually talked about at those meetings...
I will also suggest does the minor inconsistencies matter in a galactic stage? Yes they are very frustrating to the die hard fans, and ideally should never arise, but the birth planet or rank of a character rarely impact on the main plot.
Honestly? No, most don't. However, some really do. The Legion sizes for example were not settled until after book #12 (A Thousand Sons
being the last novel to use the ~10k average). When the average Legion size was subsequently clarified to be 100k (up from 10k) there was the significant issue of scale within the context of the earlier novels compared to the later ones. Seriously, how hard would it have been to discuss these glaringly obvious issues prior to starting the series? Or maybe the authors should have just read the Collected Visions
like the rest of us and learnt a thing or two.
Or what about the monumental fuck-up that The Outcast Dead
proved to be in terms of the timeline?
When authors get simple things wrong - like Legion armour colour, individual Astartes ranks, the heritage of particular Astartes and confusing 40k terms with 30k ones - its frustrating, but ultimately doesn't have a huge effect on the series. But when it goes further than that and more fundamental mistakes are made, it just gets incredibly annoying. Especially considering these mistakes could so easily be rectified before publication.