How does filterOptions work on upload fields?

I've read the docs for this (

), but I still don't get what's possible with this and also, it doesn't seem to work as I expect it to.

I have a

collection which accepts any file with mimeType

.

Then I have an upload field in a global, which looks like this:

                {
                  name: "brand",
                  type: "upload",
                  relationTo: "media",
                  filterOptions: {
                    mimeType: { equals: "image/svg+xml" },
                  },
                },

I expect it to:

1. Filter out the possible options when choosing from existing uploads in the

collection and show only svg files.

2. Prevent the user from uploading (and then saving) non-svg files.

It doesn't do either. When choosing from existing, it shows all the images, both svg and jpegs and the user is able to select a jpeg and then save the global. And the user also is able to upload non-svg files, which in turn let's the user also save the collection (which should be against the rule set by filterOptions).

What am I not getting here? What can the filterOptions actually do and if it can't do what I'm expecting, how can I do it so that the only possibility for this upload field for both uploading and selecting would be svg files?