Everything about this rumor seems plausible to me aside from the name and the addition of curved glass on a device that will “mostly retain the 5s’s design.” The name “iPhone 5se” is terrible, why wouldn’t they simply name it iPhone 5e? Has everyone at Apple forgotten about the response to the iPhone 3GS?
As for the design, wouldn’t Gurman’s sources refer to it as a miniature iPhone 6 rather than as a modified 5s? Other than the obvious size differences, the 5s’ chamfered edge is one of its few defining features when compared to the iPhone 6.
I’m typically inclined to believe Gurman’s rumors, and this one is no different, but I’m still left with questions about what form this 4-inch device will take.