Going gold for a video game means the game is finished and ready and can be printed into its Gold Master Copy.
The games industry, while note sales thresholds, do not reward sales thresholds.
Xbox at a time would re-release titles that were large sellers on the original Xbox and Xbox 360 as “Platinum Hits.” Which may have helped your confusion on the topic.
7 Days to Die, Escape from Tarkov, Wasteland 2, Pathfinder: Kingmaker, Cities: Skylines, Dungeons 3, Cult of the Lamb, Endless Space 1 and 2, Outerwilds,
They came out around peak indie craze, 14 or so years ago. I believe they were just behind Minecraft in terms of success. Total lifetime sales for their game have it outselling Skyrim.
Estimates for Steam is roughly 4.9 million sales. That data comes from peak players, average weekly players, and achievement tracking information.
Estimates taken this way usually skew higher than they really are, but the data for the current active and peak player estimates look good. As they have dropped to a quarter of weekly players.