Honestly, that's pure bullshit. For my machine, Apple advertises 12 hours of web browsing. They document (with a footnote) that those 12 hours were measured with the brightness set to medium (8 steps). With the current available display options, you can set your display brightness to a value which makes it impossible to reach the advertised battery life, and the FTC obviously doesn't come after Apple for that. Why the hell would the FTC start coming after Apple if you could get even less battery time by cranking up the brightness even more?

I don't know what you mean by the CPU being "underclocked", these machines don't have Intel CPUs with a base clock you can compare against. But the MacBook Pro machines are certainly capable of draining their batteries very quickly if you try, and they get quite hot in the process. Because having a whole lot of CPU and GPU compute is the very point of the MacBook Pro line. The battery life while spinning all GPU and CPU cores at 100% is certainly not a core differentiator which is highlighted in their marketing.