There used to be a way to report a station that was reporting bad data.
There is a station near me, KGALOGAN38, that hasn't reported any precipitation for over a year.
Yet he still proudly sports a GOLD STAR!
Although I couldn't find which readings are checked by WU, I doubt that the "gold star" analysis would include precipitation at all. I've seen plenty of heavy showers in the one half of the yard and none in the other.
Short-term rainfall comparisons even in a local area are unreliable and WU says cluster checking is over 5-day periods. I think that if rainfall is included in cluster checking, it would need to be over a longer period than 5 days.
I suspect that the big three would be pressure, temperature and humidity, followed by wind speed & direction with a higher level of tolerance. I don't base that on anything concrete, except the comparisons between my station and nearby civil airport which I accept as the local "real gold standard".