That's... a lot of stability updates.
Four distinct Switch games have all received minor updates in one evening from Nintendo.
ARMS, Splatoon 2, Super Mario Maker 2, and Animal Crossing: New Horizons have all been updated this evening (NA time). All four games listed patch notes are identical: "Several issues have been addressed to improve the gameplay experience."
The new version numbers are 5.4.1 for ARMS, 5.5.1 for Splatoon 2, 3.0.2 for Super Mario Maker 2, and 2.0.6 for Animal Crossing.