'Why does Azure Application Gateway logs originalHost_s format like "~^api\\.example\\.com$"

In the logs of my new Azure Application Gateway I notice a significant amount of entries that have a value of ~^api\\.example\\.com$ for the originalHost_s field, with no value for any of the requestUri_s, ruleName_s, listenerName_s, backendPoolName_s, backendSettingName_s fields. So I wonder what these requests are?

I have set up the Azure Application Gateway with several listeners (like for www.example.com, api.example.com, even *.example.com) and those are working as expected, and I see good traffic in the logs for those.



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