Texture streaming memory differences when opening a map directly versus streaming it into an empty map

This might just be my ignorance, but it seems strange to me and it prompts an error. When I open a map directly and play it without involving the level streaming system, everything seems fine. If instead I open an empty map, then use level streaming to stream in that original map to the empty map, the memory requirements are different to the point that my texture streaming pool is too small. This gives an error message and visually impacts the game.

Surely I have the same textures, models, etc. loaded, so there shouldn’t be such a difference in the way it’s handled, right? This isn’t game breaking for me, as in the compiled version of the game I still come in under the 1gb capacity (it uses more in the editor), but it is worrying to me.