Game asset development is one of the places where versioning systems are least used. Not only versionong "binaries" is taxing for the system, but even game code itself (¹) is often not version tracked, or controlled at all, with more of a "cowboy coder" approach.

It all stems from most non-online games (²) being sold "as is", with no intent of supporting them long term; the moment a studio/producer gets the money, they stop caring about their user base, until it's time to promote the next game. Even games with post-release DLCs, are regularly developed this way, and they end up as a giant clusterf... mess.

If Deck Nine was the "lowest bidder", with 70-80 hours a week "crunch" months, chances are they cut corners on everything, starting with proper asset versioning.

(¹: engine code is a separate thing, which gets suported across multiple games, so tends to be properly developed

²: online games, and games with microtransactions, tend to be kept in better shape, since their income depends on them working for more than a single playthrough)