Thanks for the feedback!
I am not sure why the game tries to access the network, I may have packaged a plugin that tries to access the network. I suspect it might be the Metahuman Face LiveLink plugin, or possibly just the engine setting itself up for multiplayer functionality (even though RDR is not a multiplayer game).
For full disclosure, here is a full list of the plugins our unreal project uses:
"Name": "ModelingToolsEditorMode",
"Name": "ElectronicNodes",
"Name": "FlatNodes",
"Name": "NiagaraFluids",
"Name": "RigLogic",
"Name": "LiveLink",
"Name": "LiveLinkControlRig",
"Name": "AppleARKitFaceSupport",
"Name": "HairStrands",
"Name": "SoundUtilities",
"Name": "TickOptToolkit"
However, in testing a fresh package, unreal engine still tries to access the windows network. It might be a packaging setting that I have left enabled, or it could simply be that UE is designed for multiplayer games and tries to access the local network regardless. I will look into the cause of this further.
Also I have confirmed that the full title should only be 6.25GB when unzipped, could you have possibly extracted it twice, or included the zip archive in your calculation? I plan to upload a much smaller version after the jam is over, I expect it to be less than 2GB.
EDIT: After doing some digging, it seems like all Unreal engine projects will do this by default. The only way to prevent the engine attempting to access the network is to edit the c++ source and disable the TCP, UDP, ONLINE, NETWORK, and SERVER modules as unreal engine is a multiplayer engine.