AUR specifically breaks with Manjaro because AUR targets upstream arch as a base. When a dependant Arch package updates, the AUR package immediately updates to that new dependecy if its being maintained. But since Manjaro delays the upstream updates, this AUR package will break if its updated.

Again, using the AUR as the standard for evaluating any Arch-based distro is really not cool.

Leaving that aside, the exact thing you’ve mentioned can happen on vanilla Arch, if the AUR package you are trying to install is based on Arch packages that you haven’t received yet. So you’d have to upgrade your system every time you’re trying to update or install an AUR package to be sure.

since Manjaro delays the upstream updates, this AUR package will break if its updated.

It won’t break, it will either succeed compiling or not with the older packages. If it succeeds, no harm done. If it doesn’t, you still have the previous version.

The unlikely corner case is that the new AUR package version relies on new API/features that only exist in newly released Arch packages and you absolutely must have the latest version right now. But then you’re using the wrong distro for that.

I was desperate, because upstream Arch had some critical fixes that werent shipped to Manjaro yet.

Manjaro ships critical updates out of band, without waiting for regular batch updates.