Actually, with four Meet Up Wishiwashi on the bench and a Fighting Fury Belt attached, Wishiwashi GX has 330 HP.
Yeah, because Wishiwashi considers abilities, and that's an extra thing.
The said HP "record" observed on the GX at the center of topic stands as the "base max HP", or the given-by-card HP. FYI, the aforementioned "base max HP" does not include any possible HP numbers arising from Abilities, attacks, tools, among other added factors(including Crystal Wall-holding Black Kyurem from Boundaries Crossed(and is thus not in Standard anymore) which has a max HP stat of 300, 10 short of the Eevee & Snorlax TT card's HP) that may be added to the given number on the top right corner of the pokemon card to alter said number...
Nice old wives' rumor at article's end, WPM! Surely, everyone knows that many people fell for the "Mew under the truck" trick in pokemon Red & Green/Blue, and either proved the trick as a fake, or froze their game up by the cheating device and the Missingno.