Tested the feature that you think is wrong also in Daz Studio , and see there it acts exactly the same way. If I overwrite a texture that I have loaded with a figure in the viewport it will not change, not even if rendering it. Poser does when rendering. In DS it loads after changing the Viewport from Iray-to texture shaded and back.

Blender also acts this way. We are talking here about the real time view of the model, I do not think that you are expecting that it while moving the model it also will check or reload textures on every frame movement. This would sure cause a overload as if you were to load the model on every frame new. how long does it take you to load the full model so imagine this happens on every frame when you move it.

it is something that is found in every poser version, In Daz Studio, In Blender , you just cant overwrite a texture while it is loaded and see this in real time.