It looks like if either player is close enough to the Beamos, the other player may be targeted too even if they are far away. This continues to happen if player 1 and player 2’s positions are swapped. (In the first gif, the Beamos will not target Link if the half-block is anywhere directly between him and the Beamos.)
Videos here. The Dungeon Mode one I found by accident and the Gerudo Desert one is me reproducing it.