It didn't. They downloaded 43 GB instead of 152 GB, according to SteamDB: https://steamdb.info/app/553850/depots/ Now it is 20 GB => 21 GB. Steam is pretty good at deduplicating data in transit from their servers. They are not idiots that will let developers/publishers eat their downstream connection with duplicated data.

https://partner.steamgames.com/doc/sdk/uploading#AppStructur...

Furthermore, this raises the possibility of a "de-debloater" that HDD users could run, which would duplicate the data into its loading-optimized form, if they decided they wanted to spend the space on it. (And a "de-de-debloater" to recover the space when they're not actively playing the game...)

The whole industry could benefit from this.

> to recover the space when they're not actively playing the game

This would defeat the purpose. The goal of the duplication is to place the related data physically close, on the disk. Hard links, removing then replacing, etc, wouldn't preserve the physical spacing of the data, meaning the terrible slow read head has to physically sweep around more.

I think the sane approach would be to have a HDD/SDD switch for the file lookups, with all the references pointing to the same file, for SDD.

So you'd have to defrag after re-bloating, to make all the files contiguous again. That tool already exists, and the re-bloater could just call it.

Sure, but defrag is a very slow process, especially if you're re-bloating (since it requires shifting things to make space), and definitely not something that could happen in the background, as the player is playing. Re-bloating definitely wouldn't be good for a quick "Ok, I'm ready to play!".

I imagine it'd be equivalent to a download task, just one that doesn't consume bandwidth.

Sure it can - it would need either special pre- and postprocessing or lrzip ("long range zip") to do it automatically. lrzip should be better known, it often finds significant redundancy in huge archives like VM images.

depending on how the data duplication is actually done (like texture atlasing the actual bits can be very different after image compression) it can be much harder to do rote bit level deduplication. They could potentially ship the code to generate all of those locally, but then they have to deal with a lot of extra rights/contracts to do so (proprietary codecs/tooling is super, super common in gamedev), and

Also largely cause devs/publishers honestly just don't really think about it, they've been doing it as long as optical media has been prevalent (early/mid 90s) and for the last few years devs have actually been taking a look and realizing it doesn't make as much sense as it used to, especially if like in this case the majority of the time is spent on runtime generation of, or if they require a 2080 as minimum specs whats the point of optimizing for 1 low end component if most people running it are on high end systems.

Hitman recently (4 years ago) did a similar massive file shrink and mentioned many of the same things.