The slider to Semien was a hanger. Some of the other ones weren't. They were either sitting on it to the exclusion of all other pitches (which come on Zavala pick up on that), or he was tipping. I'd think Beckham knows the signs of a pitcher tipping as well.
Maybe they wanted the unintentional intentional walk there, and see if Vlad got himself out, but he's also one of the best hitters in baseball and his dad is the best bad ball hitter maybe ever, so...