I am the appointee for my 18 year old daughter who has combined ADHD. If the money was to go directly to her it would be spent on weed, vapes, junk food and alcohol (essentially dopamine seeking behaviour). It wouldn't even go on something somewhat useful such as clothes (she'd live in dirty, damaged or too small clothes left to her own devices). Even she admits this. Instead, the money goes on additional tuition (even then, we're in debt due to paying for external tuition since she was in primary school), transport costs to college (she is 2 years behind her peers), therapy (currently not receiving but she engages periodically) and all the other costs which are subtly (not obvious to many) related to her condition. I just had her review, and continue to be appointed to manage her money. We are currently looking at how we can use the money to make her more independent and facilitate her getting into college, to appointments etc. herself.
I was really worried about what would happen to the money when she turned 18 as, not only did I think it wouldn't be used for the purpose it was intended for, it would have actively been detrimental to her wellbeing (see aforementioned things she would spend it on). But I was surprised when she seemingly understood what the money was spent on and how we were looking at using it more to support her independence. I'm hoping beyond hope that by the time she finishes college in 2028, she will be in a position to become independent and manage her own money.
Obviously ADHD is different to Autism, so I may be barking entirely up the wrong tree, but have you had the chance to sit down with him and explain what the money goes towards, and how PIP is to be used for supporting his independence and additional costs related to autism (and not games)? Although, as above, a social worker or someone in authority explaining it may have more impact.
And everyone who seems to be judging the OP - as long as she has been honest and transparent in both the application/review forms, her justification for wanting to be his appointee, and is spending the money on his best interests (which includes the additional household/daily living costs associated with his condition), then she has nothing to answer to you about, regardless of your opinion of how PIP money should be spent or managed. Your irk is with the DWP, not with the OP.