You're right, hundred is probably abetter number. But what benefits does this really bring to the table with an extra 176 pixels vertically? That's it? That's what they'll tout as 'revolutionary 4 inch screen'? Meanwhile, without getting any real improvements with that slight elongation, what it will do is fuck with developers anew. And for no real good reason. If it was a 3:2 4", the size increase would actually be beneficial to develop for.
it brings a bigger screen - you know, like people were saying they wanted. Why does it matter how many pixels it has? An entire row of icons seems a reasonable amount of additional real estate.
You can either see more of a column in a web page without scrolling, or more of the page behind the keyboard, or get an extra row on the keyboard (eg for easy access to numbers) and still have more space behind it. Or view in landscape and get more text per line to read without moving your eyes so much (assuming safari keeps the font size)
Then you can watch movies larger while keeping the aspect ratio (some will still have bars but they'll be smaller than before)
And all without increasing the width of the device which people were concerned about (pants-compatibility) and only increasing the height slightly.
People are way overblowing this TBH
a lot of this is down to apple trying to satisfy a growing market. Maybe they just need two phones? A small one for those that want compact, and a larger screen one for those that feel they need 4-5" screens?
edit - Think about accessories too - if they significantly increase the width, it'll mess with a huge number of docks that are on the market. Going taller keeps compatibility with them (even if they go small connector you could have an adapter)