I got that, but why not just a bar chart? Is there something I should be learning from this design to use when I share information professionally? Because right now if I were to chart data in this format for work I'd raise a lot of eyebrows, and I'd like to know what the advantage is.
(For context: not a dataviz expert by any means, but I've done a bunch of work in that space for the last several years.)
For sharing information professionally? Not much - but you have to remember the context. Du Bois and his team were preparing these visualizations to be shown at the World Fair in Paris, not for a business meeting. As important as the data they portray is their underlying goal: to show that African-Americans are the equals of their European / Caucasian counterparts in cultural and intellectual endeavors. Presenting the ongoing socioeconomic plight of African-Americans as Modernist data art - at a time when Modernism itself was only just starting to spill over into the visual arts - definitely supports that goal.
Now, on to the visualization merits of the spiral. We have four data points spanning two orders of magnitude. To show those on a bar chart, you'd have to either: a) use a logarithmic scale, b) use a linear scale and accept that three of the bars are tiny, or c) use "scale breaks". Instead, Du Bois presents the data in a way that draws attention to the most prominent data point, while still preserving linear scale.
There are some highly effective techniques in the other visualizations as well. The property valuation chart uses annotations to provide narrative context. The freemen / slaves proportion chart uses filled-in space to lend it a stark visual weight that, again, speaks to the narrative impact. Data visualization is storytelling with data, and these charts are clearly designed to get their narrative point across - quite effectively, I'd say.
Finally: Tufte was printed in the 80s, nearly a full century after these visualizations. That, more than anything, makes these striking. With the exception of Playfair's charts, Oliver Byrne's treatment of Euclid's Elements, certain railroad timetables, and few others, the world hadn't seen much in the way of truly effective visualization. They were literally inventing effective visualization techniques. That we don't hear more about Du Bois' charts is unfortunate.
A linear bar chart would have the red bar be 10-20x as long as the other bars. That is a "correct" visualization but looks visually quite different from what was conveyed here.
No, you probably shouldn't be learning from this design; it requires significant skill and imagination to deploy interpretive graphics like this. Stick with simple things.