I answered your question but you obviously didn't get that. My theory is that you simply don't understand the difference between internet banking and mobile banking in Thailand when it comes to functions.
We're talking about a UK phone number and the guy is in Thailand. That option is normally used for a Thai number. (I get my notifications by email.) So,why would it be useful in this case?
He might have had that account a while when it was officially possible to open an account on a tourist visa. My first bank accounts were opened on tourist visas.
Because several Thai branches prefer foreigners to use mobile banking and they don't even inform customers about internet banking. I've had Thai bank accounts before mobile banking even existed in Thailand, meaning I can use internet banking if I want with both KBank and Bangkok Bank.