The question was "How different are Blink and WebKit these days?" and "But perhaps that has changed?".
My answer was "they are different" and implicitly "yes", partially because of the heavy development work that has been done since the fork seven years ago.
If you look at the featuresets and when they introduce features I think it's reasonable to conclude they have diverged enough that they can't just pull patches from each other.
Also, there was a webkit mailing thread back when they introduced their cut-down version of service-worker that said that most of the code from blink was basically unusable for them because of the differences.
The question was: What are the differences?