FWIW, I tried the waterless approach many years ago (with straight ethylene glycol, not the Evans mix as I don't think they were even in business then), with a TR3A. As noted above, the engine ran much hotter with the waterless coolant (so hot that the temperature gauge was quickly ruined from being overheated), but never boiled over. The experiment eventually ended in disaster when the engine swallowed a valve.
IMO using the waterless coolant was not the cause of the valve failure; but the problem causing the engine to run hot (overly lean mixture at cruise) was. All the waterless coolant did was let us (it was my Dad's TR3A) continue driving the car without finding and fixing the underlying cause(s) of the persistent overheating.
So, again IMO, it is a Bad Idea to use waterless coolant to cover up a cooling problem. It probably works OK if the car didn't have problems before, but it doesn't magically fix existing problems (which can bite you when you least expect it).