If you look at the code you'll see the X tick labels as:
var ticks =
If you use a log scale, the log value actually represents the number of significant digits in the percentile. E.g.
And 1/(1-0.9)=10, 1/(1-0.99)=100 etc... and log(1/(1-p))=number of significant digits in the percentile.
log(1/(1-0.9))=1, log(1/(1-0.99))=2 etc... So that log value is particularly useful for spreading out the X axis evenly based on the number of digits in the percentile.
To be short, if you want to plot all percentile values and have a nice view of the details at higher percentile precision, you would then use a series with X = (1/(1-p)) on a log scale and Y=latency.