I think that the idea of cheating should only come into issue in brewing when there is something to be gained from it, i.e a competition medal, cash or gift prize, etc. He is an example to demonstrate my point. Two people enter an identical style beer into a competition. Part of the judging process is on the appearance and lasting effect of a good head. Person A adds nothing and person B adds a heading agent (that actually works). Naturally he should disclose that added ingredient because he is entering something artificial to intentionally make his product superior. If he does not disclose it, that would be cheating.
If someone is brewing for their own consumption and has nothing to gain, in my opinion there can be no such thing as cheating. For me cheating comes in to play when you try to gain something of value and do not disclose whatever it is you have done so you can be judged on the same playing field as everyone else.