ENGINEERING ANSWER
Equal physical length does not always mean equal electrical length. Different widths, bends, dielectric environments, launches and layer transitions can produce different phase delay.
What to decide before release
Use phase rather than length as the actual requirement. Keep geometries comparable, model dispersive behavior over the operating band and choose a measurement reference plane. Store the phase budget with the layout revision.
Checks to put in your design brief
- Define the allowable phase error and band
- Keep route environments comparable
- Measure assembled-channel phase
Important distinction
A single-frequency quarter-wave calculation does not describe broadband phase tracking.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.