This is a bias that occurs mainly in media. With lowering attention spans, media institutions are forced to summarize and condense news to make it more appealing to its readers. But summarization comes at a cost. The content loses context and that can have a big effect on how the news is perceived by the reader. Summarization also means that something has to be omitted. Different view points can portray a news story in different ways. The choice of omission can depend on the institution and the biases built into it. The other end of the spectrum are books. They offer a lot more context and background information on a particular topic or issue.
This bias has a political application as well. Politicians and campaign managers can focus on certain issues and leave out nuances. This then trickles down to other media like Twitter or Sound-bites. Concision bias is at the center of the whole "right-leaning" and "left-leaning" media discussion. They lean by leaving out some parts of the story.
