Whether or not a guy tells a friend that he is in a relationship depends mainly on their personality, relationship with their friend, and their perception of privacy. Here are some possible scenarios:
1.Privacy: Some people are so concerned about personal privacy that they may think that dating is their own private affair and there is no need to disclose it to everyone. In this case, it is normal for a guy not to tell his friends that he is in a relationship.
2.Relationship stage: If the relationship is still in its infancy or unstable, the guy may choose not to tell his friends for a while, so as not to explain again if there are changes in the future.
3.Personality differences: Some guys are introverted or low-key, and they may not like to share their private lives, including romantic situations, too much in their circle of friends.
4.Degree of trust in friends: If a guy is not close enough to certain friends, or if he thinks that some friends may react negatively to this, he may choose not to tell them.
5.Cultural and environmental factors: In some cultures and environments, relationships are seen as very personal and sensitive things, and people may be more inclined to keep them secret.
In general, it's not necessarily abnormal for a guy not to tell his friends that he's in a relationship. Everyone has the right to decide what personal information they want to share and keep.