tattoos are hearsay exceptions - but why?

In which Washington is discovered to be taking a walk on the wild side when it comes to evidence.

In Washington state, statements of fact concerning personal or family
history contained in tattoos are exceptions to the hearsay rule where the unavailability of the declarant is immaterial. Washington's ER 803(a)(13) is identical to the Federal Rule of Evidence, with that one exception.

The state Comment to this rule blandly observes: "Tattoos have been added to the items enumerated in the federal rule. The drafters felt that tattoos often reflect personal or family history and are apt to be as trustworthy as the other items listed in the rule."

That got me to thinking (I love the rules of evidence). The "declarant" in this case is presumably the person displaying the tattoo, not the tattoo artist. So the witness comes in and says, "Yes, John has a tattoo on his chest that says, 'My Heart Belongs To Daddy,' " that is not hearsay. But wouldn't the observation of the tattoo be a present sense impression of the witness testifying about tattoo? I really wonder about the necessity for this deviation from the FRE.