You heavily implied presentation preparation implies zero productivity. He tried to say this prep is also productive even if you personally don't or can't appreciate it.
I meant my other productivity drops because I am not a natural presenter so even though I am rehearsing / editing for 2 hours a day, the presentation consumes me / overwhelms me that I can't even focus for the remaining 4 hours or 2 hours. Just do the bare minimum email processing, just survive. Everyone knows it. But by being in that zone of paralysis, I can still deliver a presentation. Sometimes good sometimes ok.
I have this need for the presentation content to reside in my memory cache and other work disrupts the cache quite badly.
But that's not a way to live. The other work stalled for 3 weeks.