They probably tried and failed. IIRC the original Ark was build on a pre-release version of Unreal engine 4. There were probably loads of things missing or broken in that engine. When they couldn’t make UE load assets from a shared storage location, it was probably just easier to ship all dinos with every map.
I seriously doubt that. Assets handling is one of the most important things in a game engine, and not having to duplicate every asset for every map, including for entitlements reasons (e.g DLC ownership) is an extremely basic feature.
It sounds more like they seriously misused blueprints and/or DataAssets. To be fair, epic games did say a bunch of sightly misleading things about them when they released the engine to the public, but anyone using the engine noticed that blueprints could dramatically bloat your install size and/or memory usage in some situations, and found some workarounds.
Also they really should have been following the engine’s updates. Now I wonder if they’re the reason why Epic insists that we should really avoid being too far behind the “current” engine version for games that are actively maintained…
Source : been working with UE4 (and 5) professionally since UE4.12