Reality Check! Is "Bootlicking" Literal?

I’m familiar with the terms “spit-shined” and “spit and polish”.

But I just read an Internet comment in which the person claimed that when he left his small town, arrived in the Big City, and got a professional shoe-shine, he was horrified to see that the shoe-shiner literally licked his shoes in the process-- i.e., spread saliva on the insteps with his tongue.

The point of this comment was that he never realized that “boot licking” was literally a routine practice in the bootblack trade.

I’ve never had a professional shoe-shine, nor watched one except for a passing glimpse. I’m skeptical. Maybe a perfunctory p-tu now and then-- but licking shoes all day?

Is there any truth to this assertion, past or present?

Video evidence.