No.

Yes.

I can control what action the enemy takes, but unless I'm blatantly bending the rules, I have no control over whether or not it's a good idea to take that action.

Yes you do. Your enemies don't have the knowledge you do. This is not an opinion. It is a fact.

The enemy can choose to ready an action to shoot the owl when it leaves cover. If it does so, the player is smart enough to not send the owl out of cover into the readied action. So the owl doesn't get to use the Help action, but also the enemy ends up not doing anything meaningful with its action.

And again, this means your choice negated the owl's additional help. Therefore, it did something meaningful with its turn. This isn't an opinion. It's a fact.

Alternatively, the enemy can choose to shoot one of the PCs instead. Now, the player can send out the owl and take the Help action, but also the enemy got to shoot at a PC, thus doing something meaningful with its action.

Attacking any ally that aids in combat is meaningful. This is not an opinion. It is a fact.

This is true whether there is 1 enemy, 10 enemies, or 50 enemies. That one enemy is always better off shooting a PC than preventing one PC from getting an advantage on one attack.

Only if your entire goal is to always tpk the players, and your enemies somehow never have variation in combat goals, intelligence, personality, etc. Sounds incredibly boring. That's an opinion. You are entitled to pay vanilla enemies and boring combat.

And lastly, again, this thread is purely about HOW to kill a familiar. You saying it's "not worth it" is honestly not even relevant to the discussion at hand.

Go ahead and argue, but you're only arguing against facts because you're a poor DM who doesn't understand the rules and has all enemies share a single, boring, and incorrect optimized mindset.