Well, the check may indicate how intensive the current write to swap is. Normally if I do a manual check right after a fresh swap, it will indicate >0% fresh swap written.

But I agree with you that this may not be very useful; to me that's more of a curiosity and possibly to detect if there is a intensive process running that I don't know about.

So I guess it comes down to what is more valuable to the user, the percentage information or the time to do a check.