Non-made up numbers from Vermintide 2 (same engine): On PS4 when an optimized build took around 1.5 minutes to boot to main menu, the unoptimized version would take 12-15 minutes [1]. A different benchmark than SSD vs HDD, but shows that the optimization was certainly needed at the time. Though the PS4 was partially to blame as well, with it's meagre 5400 RPM spinny drive.

For their newer instalment, Fatshark went with a large rework of the engine's bundle system, and players on HDDs are complaining about long loading times expectedly. That game is still large at ~80GB, but not from duplication.

[1]: https://www.reddit.com/r/Vermintide/comments/hxkh0x/comment/...