Entities being ridden and controlled by skeletons do not face at their targets. This is noticable when fighting a skeleton riding a mob after being summoned by commands (e.g a pig being ridden by a skeleton).

To reproduce

1. Run the command

    /summon minecraft:pig ~ ~ ~ {Passengers:[{id:skeleton,HandItems:[{id:bow,Count:1b}],ArmorItems:[{},{},{},{id:target,Count:1b}]}]} 

2. Go to survival
   → The skeleton controls the pig, starts strafing, the pig is not oriented properly while the skeleton strafes.