Based on Barron's claim that they (not Buffett directly but one of his people) accumulated this side stake mostly in 2016-2018, they got a 5.5x result on these

Based on Barron's claim that they (not Buffett directly but one of his people) accumulated this side stake mostly in 2016-2018, they got a 5.5x result on these shares roughly speaking. So selling half sounds fair as profit taking, from a manager who may not be in the "hold forever" school of thought.