I assume its less about what the mods do and how the mods are doing it. It's an always online game (whether you think this is a bad thing is a separate issue) and there is a PvP component, which means things are going to be more locked down from a mod/cheat perspective.

The article itself says the same thing.

In a way, this does not really surprise us. After all, we’ve been constantly saying that you should be using mods only when playing a game in offline mode. And, since Diablo 4 does not have an offline mode, PC gamers should avoid using even simple mods like TurboHUD.