what are you not satisfied with... pure fact is as you have been told by such mechanic that they reduce the thread on the end of tie rod end, hence less contact thread for the tie rod to secure onto, hence theortically they are 'dangerous' more so than standard because there is an increased risk off a busted tie rod do to introducing a weakness into the suspension links
and, you have already been told that he said to use em on the track not the street because he is not liable on the track, also there is potentially less bumps etc on the track compared to average street
thats the theory
the practise is alot of people use them most dont have problems some do. the choice is urs to take the potential risk or not