This would be true in a static universe, but, during the 1.2 billion years the waves have been traveling, the universe was experiencing accelerating expansion.

For example, the edge of the observable universe is about 46.5 lightyears away, while the universe is thought to be 13.8 billion years.

https://en.wikipedia.org/wiki/Observable_universe#Misconcept...

Not if space time it'self is stretching while the light is in transit.