I am the guy in the video(3 melodicas comparison).
what I didn’t make clear in the video is that the generic no-name melodica I play also cost $100 American!
That was many maybe 15 years ago.
The Yamaha P series 32 and 37 as far as I know weren’t available or not widely available in the US at that time. At least I wasn’t familiar with them?
My thinking is the generic may have been a forerunner of Yamaha’s design perhaps a buyout or hiring away of a designer?
The one you purchased may or may not be from the same manufacturer as the one I play in the video.
My generic and my Yamaha are very, very similar especially the case, tube, mouthpiece. For the record in person the Yamaha is somehow slightly superior (the slight differences you mention are more apparent in person) I think there could be some difference in the quality of the reeds or the material they are made from.
I understand your frustration trying to find a quality instrument that in many cases you aren’t able to play before purchasing.
I went through the same aggravation and my video was a result of wanting to help others come to a choice.