If they remunerate you for those services, then you are acting as a professional. If you are acting as a professional and things go bad, you can be sued. That is why professional DMs and instructors carry liability insurance, and it isn't cheap.
It doesn't have to be money, could be a free dive. Of course, they very rarely go for this, but that's not the point, the purpose is to make sure they understand that you as a paying customer will not do their work for them for free.