My goal was to have the rule trigger when a smart outlet's power draw is >10W, change an input on a HEOS device I have integrated with HE, and then with private boolean disable the rule until the outlet power draw drops below 2W, re-enabling the rule.
It looks like you may have read some old documentation on Private Boolean. Back in the day (before you could do conditionals and whatnot), it was a way you could restrict a rule from running. Nowadays, it will only do exactly what you tell it to. As-written in this rule, that's nothing (its value isn't checked or otherwise used anywhere), but I think it's just a few clicks away from what you were going for.
For your desired outcome, I'd suggest keeping your trigger but modifying the actions, something like:
Select Actions to Run:
IF (Private Boolean is True) THEN
playInput(optical_in_1) on HEOS
Set Private Boolean False
END-IF
Wait for events: power < 2.0
Set Private Boolean True