So the discussion in the examples you provide seem to revolve around the intention of the wording of:
When you take the Attack action
and whether or not this means the forgone attack must be explicitly part of the attack action or could be a byproduct of taking it.
The good news is that in your quandry, the attack in question is explicitly stated to be part of the same attack action as you have highlighted. So even taking the strict interpretation of the rules, assuming the attack must be part of the attack action and not from it, lets do a quick checklist to see if everything works.
You take the attack action and miss with one of the attacks provided by that action. Stalker’s Flurry kicks in and provides you with an additional attack.
When you take the Attack action on your turn…
Did we take the attack action? Yes! ✔️
…you can forgo one of your attacks…
From this attack action, do we have an attack which we can forgo? Yes! ✔️
Is this attack explicitly from the attack action?
…you can make another weapon attack as part of the same action.
…and use a bonus action to direct one of your companions to strike.
Do we have a bonus action still? Let’s assume Yes! ✔️
This is actually an important footnote. Stalker’s Fury can be used on bonus action or reaction attacks too and in those cases, you would not be able to use ‘Commanders Strike’ for multiple reasons.