Yes, some of what I describe does contradict OOCSS (and other techniques too). Which one(s) you use on your project depends on many factors — such as the design, the team’s workflow, the likely rate of change to the design and more. If there’s one thing I’ve learned over the years, it’s that there are no silver bullets! Use the right tool for the job. :-)
However, whereas CSS architectures like OOCSS, BEM or ITCSS focus mainly on what kind of selectors you should use and how, making the most of the cascade is mostly a function of what properties and values you use. As such, I believe that these techniques can coexist and complement each other.