Nothing is perfect, wire located in the inner bundle curve/breakout will be shorter than the one running outside, and this can be a lot more than 3mm. The trick is, don't use the "add wire length value on node".
Usually, your bundle need to have the right length, and an acceptable wire tolerance shall be discussed/accepted with the different authorities/key player. What is most important is the final distance between completed connector, splice, breakout point. Even with the bundle, a bundle tolerance may also be agreed.
The final cut will be defined on the formboard with a connector Cut Line. When the production team cut the wire at that cut line, the connector will be at the right position and its bundle will be at the right length. Then, the wire length will be the sum of each bundle length + the length of the wire that goes in the connector (2x). Every connector in your part library will need an Add On value, and your bundle shall end at the back of the connector. (Or, no Add On if the bundle end at the TipTerm datum, or a Cut Back value if the bundle end at the front of the connector).