I was submitting a plugin earlier this evening and couldn't for the life of me figure out why the form kept complaining that my requested "Plugin Name" was taken.
The issue was that when I included the name, it was sanitized to a slug which did in fact conflict with another slug. It was also not what I was wanting my slug to be. Once I realized what this issue was, I just entered the slug I wanted and everything worked.
If it's not possible to change the field title, could we at least have a small description that clarifies what is being checked for uniqueness? This would have saved me a couple of minutes and I'm sure I'm not the only one.
Thanks!
-Dan