No, I didn't think of that Code entry character "preview" before in any way. Especially since it's only a dot appearing in practise.
It's just that I usually attempt to enter that code quickly if I have to, so I never consciously noticed it.
It seems great to me because when I enter my code slowly, I'm probably having input problems anyway (e.g. rain, thin gloves, tiredness).
And in these situations, the behavior felt so natural to me that I only now notice it.
I agree it may seem weird from a coherence standpoint, but the character appearing on keydown like it does just felt natural to me, just like a Win98 native button-down state.
These buttons don't behave like physical push-button phone buttons.
Regarding the calculator, the use case is the exact opposite, and I wasn't arguing against this regular "keypress" behavior anyway, just against the original suggested "keydown" behavior, which I'd consider a nightmare when used for tapping an on-screen keyboard.
The "bastardized" version on the iOS lock screen just has suited me well for this use case, especially when talking about numeric lock codes