execute store result entity @e[type=minecraft:armor_stand] Pose.Head[0] float 1 run scoreboard players get *y rot
execute store result entity @e[type=minecraft:armor_stand] Pose.Head[1] float 1 run scoreboard players get *x rot
execute store result entity @e[type=minecraft:armor_stand] Pose.Head[2] float 1 run scoreboard players get *z rot
Только у тебя эти значения изначально не нулевые должны быть, иначе тег не появится