Springboot - Bean selection

Hey Everyone. I Am Currently Learning Spring Boot (Part 1) and I am at “cONTROLLING bEAN sELECTION” TOPIC. Here, rather than adding @service annotation and categorizing them as primary or qualifying can we not directly put @service annotation at the interface class that is implemented by these 2 classes. I did this by mistake and I did not add @service to the implementing classes and it ran fine for me for both the implementing classes.

Can anyone help me understand if we are not using this directly