You are missing lots of points here.
It is a totally different six cylinder engine he refers to, with a larger heavier crank, more rods, more pistons, more weight.
He is primarily talking about UNDERSIZE power pulleys, which as a consequence are even lighter, he cites severe damage but gives no results/evidence.
In an ideal world there would be the same weight at each end of the crank, but try as I might I can't think of a single one where there is.
It is true that inbalance causes problems, BUT he does not offer any criteria by which he considers damage.
If you have a std engine the parts are balanced seperately as they do not know which particular pulley etc will be picked off to go with which engine, so it is all a compromise, yes it would be better if it were balanced better of course, as would any engine.
He mentions race bmw engines which are a world away from the needs of a road going rs2000 engine.
Everything doies fatigue, ie has a life expectancy, but it's fatigue is not what is going to be the first determining factor to make a crank suffer a fatigue failure, most likely it will be the engine is worn out first light years before fatigue plays a part.
No mention is made of engines that do not use a harmonic balancer, which is more than do use one.
What I am saying is it is not something that is going to happen in weeks or even years where fatigue plays a part in your engines demise.
Ask yourself how many broken cranks have you seen compared with how many that have been ruined by normal wear and tear and lack of decent oil ?
tabetha