Weasel words if ever I heard them
In my opinion waveshaping with tanh(x) as guitar distortion tends to sound OK at low gain settings as long as pre-and post-distortion EQ settings are suitable. It gives a somewhat lackluster sound, i.e. while it works, there is nothing impressive about the result. At higher gain settings it leaves a lot more to be desired, none of the liveliness of an actual valve amp is approximated by it. The circuit in the paper is meant to be a common element in solidstate overdrive/distortion pedals though, and I guess these aren't particularly great either.