The VclStyle bug is not related to diskspan. I tried to make DiskSpan create the form in another thread, the problem persisted. I ended up downloading the source of VclStyle to see how it really works and VclStyle just tries to make sure all the forms/dialogs use the same style including the ones created externally, as you can see in the video.
DiskSpan is not involved at all, I just made ISDone produce an error to show a message then I just waited to see what will happen.
https://youtu.be/0j7Lx0nxhLY
Basically, use this VclStyle library in your scripts if you know that the other libraries you import don't create additional forms/dialogs else you'll have this issue whether diskspan was used or not.