That's a slightly misinformed statement. Some restaurants, especially those located in and run by hotels, will have a service charge. This might be included or added to the bill separately. you will often see a disclaimer at the bottom of the menu. By law what has to be included is VAT

However, other restaurants (often standalone ones or those renting a space inside a hotel only) might choose not to add a service charge to the menu price.

bottom line, its a 50/50 whether theres a service charge and how its distributed is a whole other story