Note that even without the form you can still be flagged when exiting customs - I got asked a few question after collecting luggage, I think because I had my daughter's bag (she exited early with Mrs. B) on the cart which maybe looked strange. But he waived us through when I told him we only had cookies and candy. I'll take a few random questions over the idiotic x-ray any day.

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it happened to me also in ATL. On my way out from baggage claim, I was selected for a “ random “ survey. The officer was very pleasant. Followed him to side belts, opened my bigger suitcase that had some store bought coffee and chocolates. He briefly browsed through it, asked a couple of questions like address and zip code , then asked me to close the bag and exit. He was very polite the whole time. When you’re going to get taxed or fine on items, they let you know on the spot, right?

Why would you assume that? The kiosk and/or immigration officer will still ask questions about what you bought.. just no forms.

It may have been determined it was more efficient simply to ask and make an assessment based on the oral answer than trying to read the scribbles on a form, and then following-up. Law enforcement often assesses the demeanor of a person giving an oral answer to determine whether follow-up is worthwhile.

I spent Christmas in Florida last year (2019) and normally CBP forms are handed out during the flight, but they weren't, but I always use the downloadable form and fill it out on my computer beforehand anyways
When I got to the security/border bit in Tampa, the CBP guy said no he didn't want the form, which surprised me, but I'm glad, as it did cut down the time to get through security/border protection.