There are (effectively) two bases in cricket, there are always two runners on base. As you correctly stated the catcher and wicket keeper are equivalent so they are covering the batters base and it’s a standard cricketing mantra for either the bowler or nearest fieldsman to get to the stumps at the bowlers/pitchers end if there’s any chance of an out at that “base”.
(and I use the terminology of always two runners on base for cricket because the batter can be dismissed run out or stumped without leaving base)