Not necessarily a rules question, more pointing something out and seeing if I have this correct (and leaving it for some random person looking for this specific thing in the forums). Using a lion as a convenient example, but the same could be said about anything that has Grab/Push/Pull plus some other unique action/activity.
So let’s say a lion Pounces and hits with its jaws at the end of the Pounce. By the laws of subordinate actions, the lion could not follow up the Pounce with a Grab since the previous action was not a Strike like Grab requires, but an action that included Strike as a part of it.
Do I have that right? I feel like I have that right.
You don't have it right.
Here's an example from a similar feat (from your link):
"...Sudden Charge is an activity in which you use both the Stride and Strike actions to generate its effect."
Notice Sudden Charge is the option being taken, the "action", though it's better to call it an "activity" to distinguish. Even though the character doesn't opt for the generic Strike action, the character who does a Sudden Charge still counts as having made a Strike action.
Note that Grab (et al) has to have the Strike (sub)-action be the last (sub)-action taken. This means Grab works fine with Pounce & Sudden Charge because those end on a Strike. Some other activities w/ a Strike don't end on that Strike. Ex. Knockdown which ends on a Trip so you couldn't Grab after doing that activity despite the activity being your last and having a Strike within it.
You don't have it right.
Here's an example from a similar feat (from your link):
"...Sudden Charge is an activity in which you use both the Stride and Strike actions to generate its effect."Notice Sudden Charge is the option being taken, the "action", though it's better to call it an "activity" to distinguish. Even though the character doesn't opt for the generic Strike action, the character who does a Sudden Charge still counts as having made a Strike action.
Note that Grab (et al) has to have the Strike (sub)-action be the last (sub)-action taken. This means Grab works fine with Pounce & Sudden Charge because those end on a Strike. Some other activities w/ a Strike don't end on that Strike. Ex. Knockdown which ends on a Trip so you couldn't Grab after doing that activity despite the activity being your last and having a Strike within it.
That's...not what it says, though. It says that the last action used was a Strike. In a hypothetical example where a fighter, for some reason, has the Grab ability and the Sudden Charge feat and he used his first two out of three actions to Sudden Charge, then the action immediately prior to the third wasn't a Strike, it was one half of a Sudden Charge, so it doesn't meet Grab's Requirements.
Which is why I point to this quote:
As another example, if you used an action that specified, “If the next action you use is a Strike,” an activity that includes a Strike wouldn’t count, because the next thing you are doing is starting an activity, not using the Strike basic action.
Yeah, the example is using a "rider action" prior to the effect, but I don't see why it wouldn't still stand if the "rider action" in question happened after the required Strike (as is the case in Grab) rather than before.
No. What we're seeing is how awkward the overuse of "action" in PF2 lingo makes talking about them difficult.
The previous activity was a Sudden Charge. It cost two units of actions out of the creature's action pool. If one were to ask what occurred during the last action unit before the Grab, it'd be an indeterminate portion of "Sudden Charge".
For example, let's say a creature started a Sudden Charge and during the first Stride was disrupted. They'd lose both units of actions, not simply the first one, since the feat lumps them together in one activity (which got disrupted).
If the creature succeeds at the Sudden Charge, then the last action in that activity was a Strike. It was a subordinate action, not tied to a specific unit of action from one's pool of actions, but rather to the two-action Sudden Charge package.
Sudden Charge:
-Stride
-Stride
-Strike
I understand how you want the last action spent in the round to have been spent on the generic Strike action/activity, but that's not the only way to access the Strike action.
I definitely see where you're coming from (which is further complicated by the use of the the word "action" in "subordinate action"), but I just...feel like that's not how the language was intended to be set up. I don't have any evidence to back up this claim other than what I've already said, but I just don't see anywhere where the use of the word "action" is used to refer to anything other than the literal "thing from your action pool," save for the subordinate action thing, which goes in detail about how using a subordinate action isn't the same as using the action from which the subordinate action is named. This is why I wanted to present this to the forums, to see if someone could find something better than I can.