Honestly, if I had widely used software with an enforceable EULA term which allowed me to benchmark but not publicly disclose bad results I found, it would make for even worse PR for the company: I'd be able to go to a tech industry reporter saying "I ran benchmarks on this software, and I think many people would be interested in the results, but the company forbade me to release them publicly. I will still share them non-publicly with any interested parties under NDA." Or if private dissemination were also forbidden, I'd change the wording accordingly.

The better way for a company to handle this concern, if they feel it's important, is to proactively run and release benchmarks including commentary on the results, together with everything necessary for anyone to reproduce their results. Even better if they fund a trustworthy neutral third party to do this instead, with proper disclosure of the funding.

They can then respond very effectively to bad PR about badly done benchmarks. Unless their performance is actually bad, or course.