Before AI, most executives probably skimmed the summaries of written work where such summaries existed. Where summaries didn't exist they probably either didn't do the reading, sent it back to get a summary, or had to schedule some meeting with whoever produced it.

Now, they probably simplify that last step into generating an AI summary.

I can see this being interpreted as making them more productive, and in some cases that might even be true. I doubt there's an analysis of how often the AI summaries are poor quality (compared to human-written summaries). I doubt there's an analysis of how much time is wasted (and by whom) if the AI summaries mess up something important. I doubt there's an analysis comparing the benefits of having a team present its work/be questioned on its work vs. having AI simply summarize whatever they've produced.

There are also probably some superficial time savings in the form of "AI, write an email to this subordinate asking them to do XYZ." That also may save some real time in some cases, but produce externalities or extra work for other people that your executives simply don't see.