I disagree. If he works for free he still gets to build his portfolio, gain experience and expand his network in the crypto space. I think this approach is smart for someone who does not have work experience or is trying to build up a skill.
You are right there, if his only real purpose is knowledge and experience, for now, he can make a service for free, that's all, the quality of work is questionable. And he may not improve the job because it is free and the result will not satisfy the person he will serve. Anyway, that's up to him.
It is even better for him to prioritize highlighting his digital works/skills in case there are any.