is that incentivized in any way?
I'd say its probably best to avoid thinking what's best for the moderators in terms of getting paid, and just use common sense when reporting. So, if the thread is fairly obvious what needs to be removed or the user in question is a mass spammer, then its probably more time efficient for both the moderator, and yourself to just report with a "check post history" rather than going through their entire post history, and reporting it.
Same as threads, sometimes with obvious cases its just best to report one post, and indicate there's more posts like it in the thread. For example, a lot users do this with bumps.
Also, sometimes when reporting consecutive reports some users report each post, when really only one needs to be reported.
The way staff are paid can't be perfect though as it doesn't take into consideration PMs reported and issues handled with that. I've suggested before that PM reports should also go into a queue which can be handled/marked bad like current reports are. Hopefully it will be on the new forum.
I always assumed they went into the same queue as traditional reports. I'm assuming that its the default way that SMF handles these types of reports, and its too much hassle to change rather than it being intentional?