I agree with you. The mid-term trend is a great idea, but it is not enough to build a system.Those lines look to be drawn simply from bottoms to peaks.
You'd have to wait a month or so to be able to draw them, to know that the trend has finished.
Whereas a trendline, drawn under the the whole trend, with a minimum of 3 contact points, gives at least some sort of forward guidance of where a trend may go.
