In common terms it is about the Support and Resistance Lines, but in PFT it is wider and refers to the reliability of the micro (local) graphical model. Example: scale 3 shows us sharp Amplitude Increase but lower tangent became unreliable and can't be Support Line (and market confirms it by easily penetration through that line). But at scale 4 lower tangent is more reliable and may be a boundary of the real channel. In general words, the last tangent in configurations with Amplitude Increase can't be a good estimation for the channel. (Full version of the article about Price Flow Theory and Price Flow Analysis will be posted in "Technical Analysis" soon).
It must be more clear now: channel at scale 4 has almost finished u-turn UP at the expected level absorbing by the way all fluctuations, blue line on scale 3 is a previous tangent which is not a channel border P.S. have no idea about who Jack Hershey is but probably it is good for both of us