I'm partially convinced of the other interpretation.
You have 'unusual load types' and 'unusual duty cycles' listed explicitly, and 'and so forth' extending that list to other unusual factors that are similar to load types or duty cycles. The defining feature of this class is that they require oversized conductors or permit reduced sized conductors. This seems to make it clear to me that the 'marked full load current' can reasonably take into account the fact that in a machine most motors may not be running at full power most of the time.
Where I'm not convinced is: I don't believe that the NEC code tells us how to calculate the 'marked full load current', it simply requires the nameplate with the marked current so that the correct sized conductors can be chosen. I believe you would need to go to other standards or perhaps engineering practice (rather than code mandated standards) to figure out how to calculate the 'marked full load current'.
-Jonathan
