Is there a secret trick to getting the Conversation block to disable file attachments in 5.75?

I thought I could disable it by un-checking the "enable file attachments" box and saving it, but it keeps reverting to the default/enabled status. I'm not really sure why someone would think this feature should be enabled as a default, but that is a whole other issue...

I also tried editing the core_conversation block, but it didn't make a difference. I even removed the file attachment option from the form but it still shows up. And yes, I tried it as a non-logged in guest user and it let me upload. This should be a no-brainer, but I'm stumped.

Maybe I'm looking in the wrong block, but it should really be something that the user can easily check/un-check.

Does anyone have any ideas?

Any help is appreciated.