That's a good joke that Apple wants you to believe.
It's not that secure and can be foolled very easy. Any of your siblings or even total strangers that resemble you a little can unlock your device.
That is not possible with fingerprint technology.
I happen to think you're right... and you're wrong.
Who can unlock your phone with TouchID? Someone with similar fingerprints.
Who can unlock your phone with FaceID? Someone with a similar face.
Who has fingerprints that resembles yours? Total strangers.
Who has a face that resembles yours? Close family members.
I totally believe that FaceID is far more secure than TouchID. With that said however, you're far more likely to come across someone with a face that resembles yours than someone whose fingerprints resemble yours. Just because we're hearing more stories of people unlocking other phones does not means it's less secure. It just means they're having an easier time tracking down that 1-in-1,000,000 person than they are tracking down that 1-in-25,000 person. It's easier with FaceID because they already know the group most likely to beat the odds. You can't do the same with a fingerprint. There's no way to identify a group of people who are likely to have similar fingerprints. If that were the case, I suspect we would hear a LOT more stories about TouchID being defeated.
I'd say among close family members, TouchID is
might be more secure than FaceID. But I'm not really as worried about close family members getting into my phone as I am total strangers. Among the general population, I still think FaceID is as secure as they claim it to be (until I see evidence suggesting otherwise). So I'm fine with my sister unlocking my phone if it's means I'm safer at work or if I loose my phone. I can manage my sister's access easier than I can a lost/stolen phone.
Finally, a personal anecdote: When my girlfriend's daughter got her 6s a couple years back, I had no problem opening it with my fingerprint. There's no blood relation at all between us. Still, our fingers are close enough that it worked. So there's your evidence that TouchID isn't the pinnacle of security either.