I think the people who don't check the model number they are buying, most likely wont notice any difference. Especially considering their last PC wasn't anyway a 7th gen device with 15W CPU.
Second thing important to remember here is that a 15W CPU doesn't really give you anything much vs a 4.5W to 7W CPU. Neither can heavy-duty workload. The main difference between these two is that when you are going heavy-duty, the 15W version will be able to carry the load a little longer (depending on heat dissipation and a variety of factors) but still dry out before you're generally done with the tasks that max these CPUs out. The chips in this range are designed for in-and-out tasking (turbo-idle-turbo), battery life and portability.
People who buy a slim & light form factor that promises all day battery life and expect that system to be cherry topped with quad core performance, are going to be disappointed with any system, because the system they seem to be looking for doesn't exist
Also, I at least, would ask: if there was a significant performance difference that would make people think "Oh bummer this was not a "real i5 ", why would Intel ever rename the chips with their brand and duly earned reputation with the Core i chips down the line?
I think that they renamed the 7th gen chips, because the new names better suit & address their upgraded performance levels!