Why are response times high when no initialization?

I have two similar user paths. The first path has only one Action which is an HTTP GET request. The second path has the same Action, but also an Init request which runs before.
Surprisingly the first path reports a response time of ~300 ms, which is pretty high.
The second path reports a response time of ~80 ms which is correct.
It seems that user paths that do not have an Init request calculate the response time incorrectly.