>Data duplication can't just be banned by Steam
Steam compresses games as much as possible, so in the case of Helldivers 2, you had to download between ~30 and ~40 GB, which was then unpacked to 150 GB (according to SteamDB[0])
In this case, the bug was 131 GB of wasted disk space after installation. Because the waste came from duplicate files, it should have had little impact on download size (unless there's a separate bug in the installer...)
This is why the cost of the bug was so easy for the studio to ignore. An extra 131 GB of bandwidth per download would have cost Steam several million dollars over the last two years, so they might have asked the game studio to look into it.
Makes sense, initial claim was that HD2 size was mainly because of duplicated assets, and any compression worth it's salt would de-duplicate things effectively.
You are missing that each update takes AGES while it tortures your disk for patching the files (on my machine it takes 15min or so, and that's on an SSD). So I agree that this is careless and reminds me of the GTA5 startup time that was fixed by a dedicated player who finally had enough and reverse engineered the problem (see https://nee.lv/2021/02/28/How-I-cut-GTA-Online-loading-times...). I still find these things hard to accept.