The store page still says 50GB
Open the Steam page for NieR: Automata right now and the system requirements list 50GB of free space. Try to install it after the latest update and Steam wants something closer to 366GB free before it will even begin the download. According to Gamereactor, the game and its DLC together occupy around 40 to 50GB once installed, so the number is a pre-download space check, not what ends up on your drive.
The trigger was small. Gamereactor and WellPlayed both report that the update only added Korean, Simplified Chinese and Traditional Chinese language support, and that it was the game's first Steam update since July 2021. Gamereactor dates it November 5 and WellPlayed November 6 in Japan time, which is probably just a time-zone gap.
What Square Enix has said so far
Per both outlets, the official NieR account confirmed the problem on November 6, apologized, and said the cause was still being investigated. No date for a permanent fix was given. The temporary workaround is to open the game's Properties in Steam, go to the DLC tab, untick every DLC entry and install the base game on its own.
Both outlets add a careful caveat. The explanation going around, that the update duplicated the full base game into each of the eight DLC packages so Steam adds up nine copies, comes from player reports. Square Enix has confirmed the symptom, not the mechanism. That distinction matters, so we are repeating it here rather than presenting the theory as fact.
Why players were so annoyed
WellPlayed notes that the update cannot be declined, and that Steam reviews turned negative after it went live, with players saying they could not install the game or download anything else. For scale, both outlets point out that Rockstar's announced install size for GTA 6 is 212GB, which makes a 2017 action RPG asking for more space look a little absurd.
Players on consoles were not mentioned as affected. This looks like a Steam packaging problem rather than a problem inside the game itself, which is exactly the kind of bug that never shows up when you launch the build you just compiled.
What a small team can take from it
An update that adds language files should not touch how a game installs. Yet install size, depot layout and DLC relationships are shared plumbing, so a change in one corner can shift another. A fresh install on a clean machine is a test worth running for every patch, even a boring one. Check the space Steam reports, check the size of the download, and check it with DLC on and off.
It also helps to keep a rollback plan for the build you just pushed. A fast workaround is good, but being able to put the previous depot back while you investigate is better, especially when players cannot skip the update.
If you only test patches by launching the game on the machine where you built it, you will miss exactly this class of problem. Getting someone with fresh eyes and a fresh install to try your next update is the sort of check IndieBug is made for.