I think that the issue, certainly as regards "trial lessons" is one of time and adjustment.
As part of a PPL syllabus (or any other kind of ab-initio) the instructor will have time to get to know the student a little, will brief them several times and the initial flights will build up to hands-on hovering over a number of flights - with hovering taking place only when the instructor is comfortable and after the student will have had a certain amount of time to get used to being in the air and to handing over the controls.
For a trial lesson this is not the case. The instructor will likely have spent little or no time with the student - in some cases they've never met before they are loaded rotors running having been "briefed" by someone in the ops office.
The student will have had little or no time to get used to being in the air and the instructor will have little time to get the feel of the student or assess how they respond during control exchange.
For a 30 min trial lesson often advertised as including trying hovering, there is pressure on both the instructor and the student.
Is it a surprise when it goes wrong?
Yes the responsibility lies with the commander of the aircraft but i think in the case of trial lessons they are often being despatched with a piece of cheese that already has more holes in it than necessary or reasonable.
OH