The feature works like this: ask Google Assistant to look up a business or restaurant and it will ask if it can call on your behalf to make an appointment or reservation. After asking for all the important info (party size, reservation time, etc), Assistant will make a call for you using text-to-speak with some eerily human ‘umms’ and ‘ahhs’ to simulate human speech.
Even back when it was introduced in May 2018, we found the AI hard to trick, so we presume it’s only gotten more refined since.