Looking at the photographs in the press of the two events in question, neither occasion looks that much like a party. Sir Keir and Co are busy washing their nosh down with a few beers in very close confinement, definitely less than 6 feet apart, while Boris and Rishi are standing definitely at least six feet apart next to a table with a boring jug of orange juice on it, so not my idea of a jolly party. If you didn't know any different and had to stick a pin in the photograph of the rule breakers, you could be tempted to stick the pin into Sir Keir.
They say the camera never lies but you might beg to differ on this occasion. Just my casual observation!