This was an undocumented change introduced with the new ward pings' system. Patch notes only tell you that if you attack or ping a ward during the first 10 seconds (while the yellow mark appears near it) it adds the countdown after you stop seeing it, but they forgot to add that you also get 5 gold.
They seem to have reduced the gold given on kill on 5 gold too, so you only get the full gold of the ward if you kill it early or ping it as soon as you see it.
You can see the first hit at the beginning of the video and the ping interaction at 0:27, 0:37 and at 0:46
https://reddit.com/link/ywybvd/video/nz0aey8hac0a1/player
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