I have no doubt it was an honest mistake, but it does seem to mean you need to check the accuracy of information you get from him. I also agree that a helpful service person is very much more pleasant to deal with than an unhelpful one.
As you can see from the diagram from the Honda manual, the original design of the top ring did not have a recess, and the current ones with the steel rail oil rings do not have a recess either. I do not know what design evolutions Honda may have followed in between those two steps. For what it's worth, all I would do myself is make sure the rings were clearly supplied by Honda and have the correct part number (which they do). On that basis I would be sufficiently confident to use them without feeling any concern. There are many designs of piston ring, and it is not unusual for an engine manufacturer to change from one to another as they acquire more service history data from engines in the field. The use of recesses relates to how the ring twists under compression pressure in a running engine, and when you consider the range of speeds and compression pressures (the latter depends on how far the throttle is open at that moment) that may be experienced, it is no simple task to arrive at a design.
