As far as I can tell, the only thing the TE product does that your phone doesn’t is record from multiple external mics at once. Almost everything in the marketing page would work just as well on your phone though.

That's a big 'almost'. The number of channels you can record is a pretty important feature on a field recorder. What I mean is that it makes no sense comparing it to an iPhone. You could compare it to a pro field recorder, that's cheaper than an iPhone, and the features are more comparable.