It's not "just the same posture", tracing means the artist just literally copied the outline of the other work (usually by putting it on top of it, like the second image shows, which is where the name comes from).
If you ask two artists to draw someone holding a bottle while smiling do you think the drawings will come out almost identical to each other? Artists go through a lot of thought process and add their on styles on how to present scenes, and that's what makes the difference in a lot of the cases.
These two cases weren't the only ones, there were at least 3 other cases from what I saw, and from what I've heard (dropped this a long time ago), he only started doing this on recent chapters (probably to meet deadlines or because he couldn't be bothered with the series anymore).
No one forced the author/artist to quit (probably was receiving a lot of pressure both internally and from the public, though). He got caught copying other people's art, felt shameful and decided to quit (that's how the official story goes as far as we know).
No Game No Life's LN artist also got caught tracing a long time ago, mostly ignored it and moved on. Though, in this case it'd be harder to just ignore it when he was dumb enough to trace from Tokyo Ghoul instead of only smaller artists.
