"Capture traffic" merely controls whether Fiddler is registered as the system's default proxy server. If you've manually configured an application (or a service) to send its traffic to Fiddler, Fiddler still gets that traffic and it is shown so that you know that it was sent to Fiddler (the only other alternative would be to close the socket and fail the connection, which would break the app or service).
To stop that traffic from being sent to Fiddler, change the app or service's configuration.
To simply hide that traffic so that Fiddler doesn't show it, the simplest mechanism would be to choose the "Hide all" option in the status bar's traffic filtering section (change from "All processes").
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