Ata certain blur size this will show up your only solution might be a clipping mask it is a bug or limitation of the effect. Also reducing the opacity seems to help as well.
But a clipping path seems to be the best way around the limitation/bug.
Definitely seem like a bug or weird limitation.
If I reduce the glow size it will indeed not ghost anymore.
Thanks for your help.
The limitation/Bug is not wierd just has to be fixed, at least not wierd by Illustrator standards.
You can file a bug report it might add yet one more report on this and they might actually fix it.