I also wonder how much of that commentary is based on aircraft without a moving map display.
With just an FMC (or if you like an old style GPS which has just a bare "CDI" type display like the ancient decrepit Trimbles) driving the autopilot, you can easily have the plane going off at some funny angle when you press NAV.
Even with an MFD showing the whole [relevant part] of the programmed route, you need to be careful about pressing NAV because the AP is likely to not quite do quite the intercept you wanted
Often, it is easier to just fly in HDG mode and manually align the magenta line with the projected-track-ahead dotted line which you get on most Honeywell displays (not some Garmins though).
There can be odd behaviour in the intercept according to how much the CDI is deflected when you press NAV.
I've certainly had plenty of "oh b*gger this" moments and quickly switch from NAV to HDG but at least with the MFD I could see where I actually was.