The competitors could not respond with counter comparisons due to the first company's license, and so instead they added their own prohibitions to stop the first company.

Some of them just adopted the same blanket prohibition, but some were more subtle, going for reciprocity rather than prohibition--you could not publish benchmarks comparing their product to others unless you could grant or obtain for them permission to also publish benchmarks doing the same comparison. Some also required that you publish complete details of your testing so that it could be reproduced.

I don't know if anyone still uses the reciprocity approach. I'd expect that there would be plenty of loopholes that someone (Oracle?) could use to get around it that any big player using it would have given up and went for a straight prohibition.