Without even addressing whether your logic makes sense, what would such a rule be used for? If it’s my chance of succeeding when I don’t state an action declaration, I’m going to be making a ton of unnecessary action declarations, and rolling a whole lot of dice.
There's no need to address it, of course it makes sense!
It would be used precisely what it says it would be used for: passive perception.
For example, your PC is walking down a street in a town. You aren't
suspecting attack, you have no reason to think there is any danger. But, you are sill looking around, hearing noises, etc.
Now, using passive perception
as it is, the DM gives you a 10+mods versus the assassin's Hide check result because the DM wants a secret roll to see if you notice the assassin or if you will end up being surprised. This means you chance of noticing the assassin is just as good (on average) as if you were
trying to be wary of danger. But, you aren't...
Of course, the DM can use disadvantage, dropping you to 5+mods, which is basically what I am saying actual "passive" (not actively trying) perception should be.
This uses the term passive in the sense you aren't actively doing something, but it is happening anyway, you just aren't focused on it. It's like breathing. You can actively breath, controlling your breath, holding it, breathing deeply. Or you breath passively and just let your body does what it does. If you were suddenly submerged and at risk of drowning,
controlling your breath is necessary! This is the same as when a PC is actually alert for danger and using Perception that way. Without that conscious control, your perception is passive, just like breathing.
When players I met see passive on their character sheet, this is the meaning of the word they immediately interpret it as. Once the idea of "passive" in that you, as the player, don't roll, it makes some sense of course. Then they wonder if it is a DM tool, why the heck is it on their character sheet when they aren't using it??? But they get it that there is a definite difference between passive perception and active perception.
So, my original point was the term passive here leads to confusion. I've seen it more often than not. Routine and Secret Checks would be a better heading for that section, and Passive Perception could then be what many people take it as up front--your ability to notice something when you aren't looking for it.
Then, you walk down a hallway and pass a secret door, which your (new) Passive Perception picks up on. You weren't looking for secret doors, but it was there.
Having
Observant apply to this sort of passive score also makes more sense. You are likely to pick up on things when not even trying--you are observant.
Yeah... right up until the time the "clearer", "more defined" rule isn't how they want the rule to be. Then they get all bent out of shape that they can't "play RAW" anymore and have to houserule it because the WotC designers "don't know what the hell they are doing."
Precision in the rules is great, just up until they define the game in ways a person doesn't like.
FWIW, I'm not actually suggesting any changes in the rules, just in the terminology, and then
adding how I see passive perception typically interpreted.
Well, best of luck trying to get WotC to change their terminology. Hopefully it works out for you. If not, you'll just have to be comfortable re-naming these mechanics yourself at your table.
Yeah, I'm not holding my breath...
Once I explain to new players what WotC means passive scores to be used as, it makes enough sense, and then they agree it should be called something else.
