Hi Tails ..... I think you are spot on the first part -but I dont recall the confirmatory logic being discussed.

The idea behind the 6% move in the BP stems from the rationale that the Bullish Percentage Averages are calculated from P&F charts with a move threshold of 6% by Stockcharts.
So that 6% amounts to a 1-point bullish reversal roughly.

I have provided a historical pic of the BPNYA going back to 2007 here : https://www.dropbox.com/scl/fi/x99fg7u5bskhqpaiy57...

Legend :
(1) Dark Blue Triangle : Reversal logic
(2) Combined with Light Blue Ribbon at bottom : <31
(3) Green circle : My own definition of absolute despair O/S in NYSE

(4) Yellow Inverted Arrow: Hand drawn marker to show points of failure ( ie whipsaw) of this one. Its not very common - as if of course the signal itself. But will happen in cascading bears.

If you look at the Bottom panel - you will see that it has a habit of failing even from very high levels ( almost double sometimes ie >60). The median line is 54.
In the end its a matter of thrust - in this better to follow something like the Zweig

Best