Well nit-debian is made "from scratch", as in its Debian for tablets "done right", with structured hacks to get things working on tablets, whereas beta3 was a evolved debian image, so beyond some borrowed hacks it shares no common code , but i guess people calling it beta4 may contribute to that confusion.

It's better to see nit-debian as a new way to run Debian on the tablets, a sortof cleanup effort/future proof solution from previous ways.