Um, no? The 336 megabyte usb installation media contains everything you need to install base Debian. Most people will want a desktop environment and other packages, they can connect to the network to download those additional packages.
Even the how-to says the network is optional.
https://www.debian.org/releases/stable/amd64/ch02s04.en.html#idm368
We got click-baited into reading about Microsoft doing shady shit with their browser default settings (again, no less!), but that part wasn’t even mentioned in the article.