The issue here is this 6'4" height listing. I mean, Luke can't be that tall.
When you try to search it on Google, Google itself suggests that he is only 188 m tall, which is 6' 2". We also listed Luke as 6'2" tall here in our website.
Basing On Luke's PhotosBasing on photos of him with his band mates, who were all listed by Google below the 6 foot line, Luke can't be 6'4". When you browse the internet for photos and videos you'll only see him being 1 to 2 inches taller to his mates in 5 SOS.
Who Says He's 6'4"
The super fans. No doubt, the ones who say he is this tall are the super die hard fans. You know as a fan you want your idol to be the most dominant person in the scene and being tall or when people see you as a tall guy they would most likely see you as a dominant individual.
Being dominant is sexy for the fans and this is why they keep pushing that Luke is 6'4" inches tall.