If you use flatpak, snap, appimage, et al, then updates have to download the whole enchilada, because that's how they are packaged. One small library update requires changing the whole thing. It's not Arch, AFAIK, but the use of containers, that requires downloading so much data. I use none of them, and while I run Debian Sid, with updates every day, they seldom run more than a few megabytes for a big update. I just got a complete upgrade of KDE Plasma to 6.7, and it was only a few megabytes. I just refuse to use any of the trendy containerized software, partly because of the size and partly because I don't trust the integrity of the packages. If it's not in the Debian repos, I probably don't need it. I do use a few packages from outside, but I'm rather selective on what and when.