The designer admits in his video that he doesn't design buildings and that it was challenging. It is not outside any realm of possibility that he looked online for inspiration and used techniques and styles that he found, even if it was sub-consciously. If you look at the list of similarities and almost exact copying of techniques that TJJohn put together its suspiciously similar.
It matters for two reasons, first its someone else's design and that would be stealing someone's intellectual property. Second reason is because LEGO is monetizing fan creations on Cuusoo and giving 1% of the sales to the fan who designs a successful product. If they are using someone's idea they should be compensated by LEGO's own logic.
By all measures this will be a successful set, its gorgeous, but its strikingly similar to another creation. I hope that there is more to this than we know about and that the original builder get credit or that this is some sort of accident. However, there is nothing wrong with people asking questions.