Necessary in what sense, correct simulation or layout? Please show your layout.
The "normal and correct" use of this includes a length of line at port 3 of the MTEE, not just the MTEE. And w3 is then the width of that line. And that is where the resistor connects.
You abuse the elements in an unusual way, and leave out many elements that are usually included in such a Wilkinson schematic - for more accurate simulation and meaningful layout.
That's what I mean with abuse: the MTEE width at port 3 is the width of the element connected there. You now connect "something somewhere", and don't care about the values. I don't understand this careless and ignorant use of ADS schematic models - why not do it properly? Models are only accurate when using them as designed, within the documented limits. For "free layout" you better use EM to simulate.