This is because the Status Overview dashboard groups the results by URL. I didn't originally design the app to monitor proxies like this. I opened a ticket to make this supported though (see https://lukemurphey.net/issues/1805).
In the meantime, you can work around this issue by making the URLs slightly different (like adding a slash to one of them, such as "https://www.google.com/").
Update
This has been fixed in version 2.1 (https://splunkbase.splunk.com/app/1493/). It now aggregates by source such that both URLs will appear.
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