Why? He’s a typographer, of course he’s pedantic. Paired with his eccentricities it’s quite entertaining to listen to him.
At the risk of flogging a dead horse, the tweeter was technically correct when she said that she had written a book. She said neither that she edited, typeset, printed, bound, distributed, shelved, loaned, sold, nor solely forged a book out of the edifice of the void.
Pedantically-speaking, Spiekermann dropped the ball on this one.