A manager that has no technical knowledge is useless, like a jockey who doesn't see a difference between a poney and a horse or distinguish a healthy horse from an injured one.
Thats taking it way too far. Sure; its useful for managers to understand programming concepts (deployment, testing, etc). But the job of a good manager isn't managing code. Its managing people. Making sure Sally is happy in her new role. Setting up a meeting between Jake and the sales team so they can get to the bottom of that important bug. Helping mediate that conflict between the software team and the design team over what features to prioritise.
A manager is hired to be an expert at humans. Not an expert at computers.