It's under 8 and above 10, yeah, but that bonus is usually negligible, since despite EZ heavily lowering the AR, it decreases the OD and CS just as much, making the map a lot easier. It'd probably help a bit for AR7/6 Insanes but I think (not sure) the bonus is mostly there for AR10.3,10.87 and 11 plays, specifically the ones higher up. I'm also going to guess that's part of the reason why DT gives so much pp. Even if 10.3 would only give 10pp on top of your total - it's still 10pp, it's the difference between a 290 and 300pp play. I don't really think AR should be rewarded that much (and it probably isn't) as pp seems to focus on rewarding for physical skills and not mental ones.
If it focused on mental skills, FL would give much more pp, but since mental skills are a lot easier to acquire than physical ones (reading/focus as opposed to streaming/jumping) they're not valued as much. AR11 should be an exception here since it requires quite extreme reflexes to be played properly. The only person I know of who can consistently play with AR11 (and do some sightread HDDTHR plays too) is Emperor, which goes to show that that AR does require a specific skill that not anyone can simply obtain.
If it focused on mental skills, FL would give much more pp, but since mental skills are a lot easier to acquire than physical ones (reading/focus as opposed to streaming/jumping) they're not valued as much. AR11 should be an exception here since it requires quite extreme reflexes to be played properly. The only person I know of who can consistently play with AR11 (and do some sightread HDDTHR plays too) is Emperor, which goes to show that that AR does require a specific skill that not anyone can simply obtain.