The original comment referred to a 'full power on stall'. If that means recovering from a fully-developed stall entered with full power, then it is perhaps unsurprising that he had difficulty as he was probably totally out of his depth!
Anyone should find demonstrating recovery from a stall in the approach configuration reasonably straightforward - but normally the recovery is required at the incipient stage only. We demonstrate the fully-developed stall in the approach configuration during Stalling 2, but it is not a requirement for any JAR-FCL LST/LPC or Skill Test.
A full power stall might be demonstrated during training to the fully-developed stage, but I wouldn't expect a PPL student to practise it. Also, due to the high likelihood of an incipient spin, I would require the a/c to be in the utility category for such an aggressive manoeuvre.
There is a balance between safe handling skills and risk avoidance. I don't see the relevance of anyone being required to demonstrate recovery from a fully-developed full power stall unless they are hiring an a/c for aerobatics.
What was the ground brief like - and was the requirement discussed properly?