Gamers being gamers though they’re not going to say “well, we on reflection I’ve not had to wait so long”, they’re going to slam you with one star reviews for the fact there’s an hour long loading screen on first start.
The recompression/decompression logic could (and I would argue, should) be packaged separately for distribution platform instead of being embedded as part of the game's logic. In the case of using Steam, it would be no different than how it shows separation of time spent downloading vs time spent installing.
This allows it to be ran automatically after download without having the user need to launch the game.
