I have no idea. I think the claim is that as "arch is unstable", the delay allows them to make sure none of that "wild instability" makes it into Manjaro. But as far as I can tell, no such checking occurs and the delay is just a delay. I got into the habit of putting off updating because more often than not it meant an evening of timeshifting and troubleshooting.

But arch isn't really that unstable. On Endeavour (endeavours main repos are just the arch repos, they don't maintain their own) I update whenever my system notifies me there's new stuff, and the possibility that my system won't boot afterwards doesn't really cross my mind anymore. I still run timeshift, but I haven't needed it yet.

In fact, if you really want stability... Unless you need some upcoming security update, bug fix or feature, you can just keep using your system, only installing things when you need them. There's no real reason to impulsively install updates the second they are available. My system doesn't even check for updates more than once a week.

Then, if my system worked yesterday, it will do say today. And unless I decide to change something today, it will do so tomorrow too.

In that sense even arch's stability is "customizable" because you can voluntarily reduce how often you risk breaking something, while at the same time running a system with still more recent packages than most other distros.