Arch is kinda the I can do everything reliably distros if you know how to set me up.
Updates are only installed when you run pacman (or a pacman wrapper/replacement). But I guess you mean changes to a package in the repository with "package upgrades straight from the developers".
There are two sources for arch packages:
- The official repository,
- The AUR repository
The later one does indeed allow maintainers to arbitrary update or remove packages. It provides just a way for _users_ to provide custom packages to other users. The responsibility for reviewing them lies with the person using them. This is clearly communicated. Also most AUR packages do not contain any code but just install instructions which pull the code/binaries from their original source (e.g. github/github releases/the website of the project for which the package is). So reviewing them is normally quote doable. The only annoying to review AUR package I can remember is tor-browser.
With regard to the official package thinks are actually pretty similar as far as I know (but I don't rally know) except that not everyone can publish thinks there and you have a group of "trusted" core maintainers.
In the end arch is a distro by the "experienced" Linux user for the "experienced" Linux user without to much financial backing.
Not that there still are thinks like a security group which tracks CVE's and similar but it's fully based on volunteers.
This makes it quite a fascinating choice as any choices wrt. maintenance comes from some dev wanting to use it on their system.
But yes if you don't trust the core maintainers don't use it.
Also it might not be appropriate to be used on cooperate systems due to company policies wrt. legal liability reasons.
Still you also trust many other software maintainers solely based on a good reputation and for arch it's in the end the same.
Also besides pacman and probably some other minor thinks Arch doesn't do any code. It's just provides code other people wrote (sometimes with publicly known patches) to the user, sometimes pre-compiled.