Isnβt it supposed to happen? It seems that also each BasePart and Union, basically every Instance with a Content property reloads, maybe except for Sounds.
During window minimization we unload mesh + texture memory as it is a large portion of memory available for the device. Once refocused it reloads.
(The part where you see the old frame with all the content for a brief moment is not common across all devices and seems to be that the driver holds the old swapchain image. On most devices we tested with you just get a black screen upon transitioning back to the app)