This sounds like pseudolegal folklore (in the US at least). Do you have any actual examples where this affected a case?

In the US, you get copyright on your work automatically, with or without a label.

The only thing a label does in the US is defend against "innocent infringement" defenses. But even that defense doesn't absolve the other party from liability; you just can't recover as much.

There is no reason you can't have `(C) 200X-$currentYear Acme Inc` or whatever.

You're right that the notice is effectively useless for such web pages. And if it doesn't matter, then why bother to put anything?

Most people do so because everyone else does; it looks off if you don't see a copyright at the bottom of an otherwise professional site.

That doesn't look off.

What looks off is showing you don't know how copyright works by blindly putting the current year.

While this is certainly a creative way to interpret the copyright notice's date, I believe most people look at it as a "last updated" sort of thing.

Yet your earlier comment said "200x-$currentYear" not "200x-$modifiedYear" in reply to someone automatically inserting the year. That shows a misunderstanding of copyright AND an intent to mislead when you believe others view it as last updated.

You're better off omitting it entirely in generated web pages. No one cares unless they don't understand copyright, the year shown isn't the current year, and they're already looking to find fault. In other words, for those that treat it as last updated, they must already be struggling to find value when they scroll to your copyright notice, and at that point, after feeling the page looks stale, is seeing the current year going to change their mind?

I'm not sure what the point being made here even is, beyond arguing just to argue?

It does not matter in the US whether you use the current year or last modified date. At worst, omitting a date entirely makes it easier for the other guy to claim "innocent infringement", which only reduces your damages. Show me one US court case from this century where the tail of a date range had a material affect on the outcome.

Moreover, it is an objective fact that people use the current year and the modified year in web pages being written today. And based on the comment that kicked this whole chain off, clearly people are using it as a signal of when the page was changed.