He was directly addressing apps that claim to do so, and proving that they can't, with laypeople who might have diabetes as the target audience.

It's more a data-driven pub test, I think it explains itself well.

The question is - are those apps actually so simplistic? Or is this a strawman.

I guess that's partially my original point summarised; I'd like to see this criticism levied at the apps advertising it - rather than using something that doesn't