I have seen this several times, but now I've tried to diagnose it. This is from an Azure WebApp. It shows a Purepath that seems to start only after some time, in this case one second:
Values vary from Purepath to Purepath, and sometimes they are negligible.
If we see the Code Level, it seems that the time is dependent on AcquireRequestState:
According to https://docs.microsoft.com/en-us/previous-versions/aspnet/bb470252(v=vs.100)
AcquireRequestState is still IIS before being passed to tha application. Checked other variables but have not been able to find anything that might explain this initial late start.
The part of purepath you have presented is related to IIS modules. There can be plenty of reasons of such behaviour, you should discuss it on IIS community I suppose. It may be related to IIS configuration, problems between IIS and .NET part etc.