Warning signs, sticky notes, fences over extremely specific stretches of grass, and similar things have become standard pieces of our narrative design toolkit.
It's an easy way to quickly, efficiently, and subtly make a player wonder what happened to necessitate that rule or restriction: Why is there a sign on the break room fridge saying that you should NEVER turn on the microwave while someone is in the elevator? Why is there a fence over just this one specific stretch of highway overpass? Is this "DO NOT CREATE THE TORMENT NEXUS" sign here because someone created the torment nexus?
It works pretty well in my experience and I've used it in my own writing. I can't count the number of times I've seen people stream games, come across a log or sign in the background or even a blood splatter on the wall near a hidden trap and say "Oh, I bet somebody put their hand in the woodchipper and that's why this 'don't put your hand in the woodchipper!' sign is here." I want to focus just on the Warning Labels and Rules aspect though for a minute, because I think they're a separate category from the bloodsplatter near the sawblade trap.
A crater in the ground or the scorched outline of a body near a flamethrower trap is direct evidence of something that happened, so it's a very direct signifier of a thing the player can trace from effect back to cause. We tend to treat warning labels, signs, logs with stern messages like 'DO NOT FLIP THE POWER BEFORE YOU REPLACE THE FUSE', or barricaded windows as direct indicators for an action taken in response to something that happened before. I've heard this elsewhere too in book clubs and media criticism in general - having a net on a skyscraper must mean someone tried to jump at some point, or having a rule against two employees being in a supply closet at the same time must be because someone was caught doing something illicit there.
But that's not really the case in our real lives, is it? We take this as a corollary that warning labels are placed in response to someone doing the thing the label warns you against, or rules to restrict you being placed because someone did that thing and there was some Consequence from it. A lot of industrial warning signs are placed before accidents occur just because it's pretty obvious to designers that touching the extremely heavy powerful moving parts will kill you, and it's not that they placed that because someone died. More to the point though, a lot of workplace rules against employee's congregating together could be management trying to preempt worker organizing even if they say the rule is because two people were caught ditching work to get high in a janitor's closet. At the level of government, so many highly specific laws (like drag bans and bathroom restrictions in the US) are made in response to fearmongering and bigotry and not because a trans person actually stalked through Floridian bathrooms like a serial killer.
We don't often take that level of critical expectation to the warning signs or log entries or environmental storytelling pieces we see in games. It serves us pretty well because most designers use it in a pretty straightforward way, but I'm always impressed when I see environmental storytelling that doesn't work as a neat and clean line that players can trace from effect back to cause. I think there's a lot more we could do with environmental storytelling and the narrative design of warning labels and diagetic rules and I've seen some really cool things come out of games that subvert player expectations that a warning label exists because someone did the thing it's warning against.