Welcome to Android Central forums. I think you may be looking at this wrong. Just a couple of questions before we go too far.
What phone do you have?
When you say that you've moved the app to secure folder, is this the secure folder app that came with the phone or one you've added from the Play Store or somewhere else?
When you moved X to your secure folder did you uninstall the X app in your main phone area? Did you uninstall or sign out of the X app?
Have you used secure folder before?
For my examples I will assume that your phone has a built-in secure folder and that is what you're using.
The point of Secure Folder is to hide an app. In this case you're hiding X and not your gallery or camera apps. X still has permission to view and select images from those places, even though they are not in SF. As Golfdriver97 said it still has that blanket access that you granted. You could revoke these permissions if you don't want it to have this access outside of SF but remember this is a one way street. It can look out but nothing can see in. If you don't want it be able to look out, remove it's access/permission to these areas.
On a side note.
If you put an app like X in SF and leave an instance of it in your EveryDay phone area, both with the same log-ins, both will display the same information. One from a secure area and the other from your ED phone area. For this to work and actually be secure, either change/create a new log-in for one or the other app or uninstall the instance of the app in the ED phone area. And yes, you can uninstall one without affecting the other. If you wanted to get rid of both you would have to uninstall 2 apps, even though they have the same name. Another thing you could do if you want exclusive images that don't appear in your ED phone area, would be to add your camera and a gallery app to SF. Those images will only be available and viewable.
I hope this helps. Let us know and best wishes.