Why does passive sensors allow a ship without lock or calculate action get a lock/calculate but an ionized ship without focus can’t focus.

3. During the perform action step, the ship can perform only the (focus) action.

... Before you engage, if your (charge) is inactive, you may perform a (calculate) or (lock) action.

Does the phrasing “can perform only the” that different from “may perform a”? Or is there a different reason these work the way they do?

passive Sensors requires you to use your action in the activation phase to remove the charge counter from itself to be able to use its other effect for a calculate or TL in the engagement phase.

Passive Sensors:
Action: Spend 1 . You can only perform this action in your Perform Action step.
While your is inactive, you cannot be coordinated. Before you engage, if your is inactive, you may perform a or action.

so if the ship with sensors is ioned, it wont be able to use the Passive sensors action (because it can only do the focus action), and its charge will be active when it engages so it wont be able to take a calculate or TL when it engages.

This wasn’t meant to be an ionized ship attempting to use passive sensors but the difference in why ships can sometimes use actions they don’t have and sometimes can’t use actions they don’t have in similar situations.

An ionized drone vs. a passive sensor phantom as an example.

Well, to my understanding, this is a very fluff-based decision. Focusing is the only action performed by the pilots themselves , not by the ship while controller by the pilot. And when the craft is ionised, the controls are blinking, handles are unresponsive, and warmings are triggered all around the cockpit - the pilot still can at least take a deep breath and brace for the worse. Meanwhile, droids and autopilots also suffer the ionisation. We all know ion weapons are super effective against droids after all.

Then, fluff aside:

1 hour ago, gibbro said:

 Does  the phrasing  “can perform only the” that different from “may perform a”  ? Or is there a different reason these work the way they do? 

Yes, it's different. As per first pages of the Rules Reference, "may" describes a(n added) option/capacity to do something, that the unit can possibly utilize.

"can perform only" is a restrictive term, introducing boundaries to the capacities the unit already had before the effect.

And so it checks out that ionised ship cannot focus if it wasn't an option for it in the first place, but another ship with passive sensors installed on board can use the new tech to do what they couldn't do before the upgrade.

Cheers!

2 hours ago, Ryfterek said:

Yes, it's different. As per first pages of the Rules Reference, "may" describes a(n added) option/capacity to do something, that the unit can possibly utilize.

"can perform only" is a restrictive term, introducing boundaries to the capacities the unit already had before the effect.

Yes, this.

Just as another example, You may perform a focus action would mean you can choose to focus, but may or may not be able to do something else (or nothing) as well.

In contrast, You can perform an action only if you are not stressed would mean you cannot perform an action unless the stated condition is true (i.e. you are not stressed). It's placing a restriction or condition on something you otherwise would be able to do.

The rule about ionized ships basically means "The ship cannot perform any action that isn't the focus action".

Okay so “may” as permissive, grants the action, if you so choose, regardless of action bar. But “can” means if you have the means to do the action then take it if you want to.

Thanks, it feels right in my head now.

3 hours ago, gibbro said:

Okay so “may” as permissive, grants the action, if you so choose, regardless of action bar. But “can” means if you have the means to do the action then take it if you want to.

Thanks, it feels right in my head now.

Pretty much, yes. Pg 2 from the rules reference outlines May, Can and Must.

Quote

The word “ can ” is used to mean “has the capacity to.” For example, an ability that says “While you boost or barrel roll, you can move through and overlap obstacles” means when a ship with this ability boosts or barrel rolls, it ignores the rules that prevents them from overlapping or moving through obstacles. The ship always applies this effect as the effect is not optional but instead an expanded capability.