I totally agree with this. "Multiple performance and stability improvements" is meaningless info for the release notes of a professional, mission-critical application like Resolve. It's not enough information to allow the end user to make an educated decision on whether to upgrade or not.
None of the "features" of 16.2.6 are of interest to me, but I am always interested in "performance and stability improvements". But if I don't know if these specific improvements will noticeably impact my work in either of those specific regards, then there's not much incentive to upgrade if the currently installed version works good enough.
Granted, these unspecified "performance and stability improvements" may be so minor that nobody would ever notice them (e.g. code optimization or refactoring), but in that case, I'd almost rather not see this as a "feature" of the new release, because to my way of thinking it should be expected that every new release has stability and performance improvements in some fashion, even if it's minor. But if the "improvements" are related to things that have been specifically discussed on this forum, for example, then those things should be specifically mentioned in the release notes, so that you can make an informed decision on making the upgrade or not.