The phrase is metaphorical, referring to perfection but not actual baseball.

Not Literal

Using it can imply very high, sometimes unrealistic, expectations for success.

High Expectations

It is casual, best suited for informal conversations or friendly banter.

The phrase comes from baseball where batting 1.000 means getting a hit every time.

It's often used outside sports to mean excelling in any area of life.

It doesn't always mean a perfect record, but doing extremely well.