More forward-looking restaurants manage this all themselves as part of their digital strategy, but it’s still a small percentage and disproportionately located in the US.
I’m not saying Google doesn’t also scrape or use other sources, I’m sure they do, but this is one of those situations where the whole system is broken. Tbh one of the bank shot benefits of having all of these digital delivery services is that some restaurants are using aggregators that can also publish menu data.
As far as the authors idea about markup for menus, that’s great, but highly improbable for a bunch of reasons: most restaurants don’t update their menu frequently, dishes are often difficult to represent structurally, POS systems are often modeled differently than the printed menus, etc.