Why is UTexture MinimalAPI?

We need to make a custom texture asset, and figured that should be pretty simple. Just subclass UTexture or UTexture2D and build on the functionality we need. Just like we did with the Cameras. Then we find the joke is on us because UTexture is marked as MinimalAPI and thus not properly exposed?

What is the reasoning behind this? Sure we could change the source, but we really want to keep those changes minimal so we can upgrade easily in the future.