Me too. I'm glad it's there. Note though Tyler's description here, Target Practice: The Target Accuracy tool is great for planning but sort of visually understates the risk by lopping off the bottom and top 15%.
Hmm, maybe I am misreading the chart. Here are the details; if you can see where I got off track, let me know.
I read the tool as though the CAGR percentages refer to the middle 70%, which does lop off the highest and lowest 15%. But in the chart itself, the middle band is shown in darker color, with little squares on the right hand y axis marking the upper and lower bound of the middle 70%. In other words, the little squares mark the 15 year result of the stated CAGRs. However, the chart also shows the actual best case and worst case in the data. These are marked by solid lines. The highest 15% and lowest 15% are not excluded, they are displayed on the chart in light color.
If it were up to me, I'd add the second box of CAGRs. I'd label the existing box "Likely CAGR". The second box would show the highest and lowest CAGR. I'd label that one something like "Highest/Lowest CAGR". Like you, SeattleCPA, I instinctively feel that the max boundaries in the data set are really important. Once I delude my myself into thinking that I understand the chart, I immediately (and worriedly) begin estimating the bottom boundary.
That said, Tyler generally manages the trade-off between clarity and info overload really really well. I usually want more data that most people can stand.
The "Worst, Best and Average" chart posted upthread is thought provoking too.