This is a damn good question. I have information here on the original Spidey heads in the corner covering the bar code but after a quick scan it doesn't mention symbiote spidey specifically https://scifi.stackexchange.com/questions/20314/what-does-the-spider-man-symbol-on-1980s-comic-covers-mean

And I had watched a video this past year on the topic of this that goes a little in depth on the reasons why this happened at all (based on newsstands and books that get returned), I don't remember the video touching on the black Spidey, but later today if I remember I want to re-watch this video to see if it does or just find this info somehow, I'm curious now.