Models that have invisible or have no parts (e.g. folders w/ values) shows up with the moderated icon, yet they are still able to be inserted.
For example:
Example
Note the ones circled. They do not contain a visible brick, yet they can still be inserted into studio
To reproduce this:
- Go into studio and create a folder and insert some values into it
- Upload the folder to Roblox
- Go into your inventory, and find the folder you uploaded
I tried it here: DevTest - Roblox
They also show up as moderated in the studio toolbox.