I know the term "I am smart like that." (without "just"). It is usual a response to a comment. John: "Wow! How did you know how to fix the car?" Mike: "I am smart like that." in that situation it means someone is intelligent in a certain or given situation. You could also say "I am generous like that." etc. It is more arrogant if anything.

It is usually..... In that situation..... Please excuse the errors.

More context is needed