I haven't personally tested policing over multiple PFEs on either IChip or Trio so I can't say for certain. However, based on what you linked to, yes. The page matches up with the Trio processing path outlined in the O'Reilly MX book and I'm not aware of anything that would change that behavior.
That said, a possible alternative would be to configure the LAG for primary/backup, in which case traffic would only flow through a single interface, and thus a single PFE, at a time. If you really need the additional capacity, or the LAG is more than two ports, then that isn't an option.
I dug a little bit further in the MX book in the Trio CoS section, specifically pages 421-423. It touches on doing CoS scheduling for a LAG interface and two different modes that are available. Scale mode takes the configured values, divides them by the number of interfaces in the LAG, and then applies that divided value to each physical interface. Replicate mode simply takes the configured values and applies them to each interface in the LAG directly. While basic policing / shaping doesn't have the same options, it does further support that the values you configure for policing will be sent to each PFE that supports an interface in the LAG, potentially resulting in a higher aggregate value over all of the LAG interfaces than you expected.
Cheers!
-Chad