Because, one of the valid dictionary definitions of "recognition" is simply acknowledging something exists. No prior knowledge needed for that, other than the generic training the facial detection software has undergone.
"Facial recognition" refers to seeing a face and knowing whose face it is. It's the difference between "that's a face" and "that's my friend Jeff".
That some constituent word has some other definition is not relevant. What you're doing is equivalent to reading "my nose is running" and thinking "egads! This person's nose has sprouted legs and taken off down the track!"
Edit: it seems the law defined the term "facial recognition" so that was the only answer I was seeking
You can do that, but I hedged my statement with:
> and expect anyone else to understand you
under which constraint, you're incorrect.
There's a relevant quote from Lewis Carroll's Through The Looking Glass:
> "When I use a word,” Humpty Dumpty said in rather a scornful tone, “it means just what I choose it to mean—neither more nor less."
In other words, to put the burden on the listener rather than the speaker to be clear about meaning, is bad communication.
No one reasonably uses "facial recognition" or "I recognized a face" to mean "I detected that there was, indeed, a face there."
In this case, the statute doesn't even say "facial recognition". It discusses storing a "scan of face geometry" such that it identifies an individual, and clarifies that an ordinary photograph doesn't count.
Ignoring context leads to things like "English as She is Spoke" https://en.wikipedia.org/wiki/English_as_She_Is_Spoke
Decent dictionaries give some guidance as to the contexts in which each each definition is applicable, but for thoroughness you probably cannot beat the unabridged Oxford English Dictionary.
The relevant definition here is neither legal nor technical, but from common usage, where recognizing a face, if not qualified, is taken to mean recognizing an individual by their face, not recognizing that you are seeing a face.
Courts sometimes adopt tendentious, cotroversial or disputed definitions in their rulings, and law-makers sometimes (and more frequently) do so when writing the law, but that in no way invalidates what I have written, which is about how to use a dictionary.