Indeed. From my understanding, while this is still technically true, they have replaced the need for users to do anything with chips in the batteries themselves which shut off recharging when they're near 100%.

That's why if you pay attention you'll often see your battery % go from 97%-100% and then back down to 97%. It is reporting as "charging" but in reality it goes idle to let the battery de-charge a little.

They do have some advice on "long-term" storage here, which is roughly along those lines:

https://www.apple.com/batteries/maximizing-performance/

They don't say what "long-term" is, but monthly seems reasonable to me.

It specifically calls out recharging it to 50% every six months, so I assume it's a month+ kind of long term.

Also Apple seems to indicate that storage in a deep discharge state is far more damaging than storage at near-capacity based on the wording.

So if you're in doubt, charge it before you store it.

Finally, I don't think there's anything on that page that says you shouldn't keep your laptop plugged in when it's at 100%. I would be very surprised if they didn't have some cycle-conditioning going on. I have both a 2008 unibody and 2010 MBP, both essentially remaining plugged in for years. I don't think the battery life is abnormally low for their age, they still are capable of several hours of usage on battery.

Or they're trying to bolster sales of their warranty initative: Apple Care