It all depends on the tone and environment You set for the session. If You clarify beforehand that the whole session is training and confidence building then startle scenarios are fine, as long as everyone gets out of the box with a smile and learning points.
Modern training is deviating from events training and moving towards competencies training. Any scenario you run can fit this purpose and it’s just a means to an end, ie. develop resilience. As pilots we need to be able to handle the unexpected rather than a set of well defined scenarios.