I didn't break the rule either, however
I too was confused by it. For example, I wondered if the things like the Sphinx, Pyramids and so on that you can photograph overseas (and get through buy debug) to raise your photography skill would count as well as the cameras for the purposes of buy debug items. However, I decided to play it safe and not get any of those sorts of items.
Items I did get through buy debug were the board breaker, training dummy and nectar maker.
If a list of the items that are considered to be skilling objects that can be gotten through buydebug were listed as part of the rules, that would then prevent people unwittingly breaking them, and would give people an even playing field.