I notice you made no attempt to explain how your claim is true. So you gave me no chance to understand what you think.
I’m not sure what “religious about their religion” means. At face value, meaning I’m not making any assumptions or guesses, this is an obscure and evasive statement.
People who are serious about their religious views, have religious leanings, and actually observe their religion are "religious about religion".
ie a person is not religious by choice but because they are religious. Just like atheism isn't really a choice but typically a person's default position.