The endpoint games.roblox.com/v1/games returns the wrong player count in response to a query. Instead of returning the concurrent players across the entire universe, the concurrent players for only the root place are returned.
You can see an example of this with Vestaria:
Website page: Vesteria - Roblox - Far more players are indicated as playing
Response from API: https://games.roblox.com/v1/games?universeIds=833209132 - Only those in the root place are indicated as playing