I work in a role where I see cutting-edge AI technology all the time, usually in prototype stages where the rollout of the full tech will happen in 3-5 years.
I can say unequivocally: yes, absolutely, facial recognition AI technology can make incredibly accurate estimates of age. It is not even difficult using open-source products and toolkits running on off-the-shelf hardware. Many companies are currently working on much more sophisticated tech than that.
If your local stores wanted to, they could, as of this year, buy a system that would identify your race, sex, age, and even whether you were wearing luxury brands (and which ones they were). They could even identify whether you were a specific VIP based on facial recognition, with a database of thousands of celebrities, and alert the staff as to your name and why you were famous.
These technologies are being rolled out slowly because people are extremely afraid of the privacy implications (with good reason, IMO). But the idea that AI can "barely detect whether a person is in a photo" is not true -- people just think it is because all they have access to is consumer-grade tech that has been thoroughly idiotproofed.