Dragging a module from a Dolphin Window to a Project moves the original file?

In building up a new version of a helper tool, I used drag and drop to add an existing .xojo_code module from the Dolphin file manager window to the project navigator. Upon reloading the original project that I dropped the file from, I’ve just discovered that the original file has been removed from the original location (Xojo prompts to locate it).

I normally drop between projects and things work as expected, but the file was already visible in a file manager window in this instance, so I tried that method. I’ve repeated it 5 times on 3 distros, so it’s definitely not a glitch.

But, since this only happens under Linux that I can determine, the question becomes - is this an issue with Xojo on Linux or with the Dolphin file manager on Linux?

Xojo 18r4 and 19r1.1
Mint, CentOS, and Fedora

Update - this is with both Dolphin and Caja