I think you’re probably right about workflow between officers being the cause of the applications being approved slightly out of sync. My OWP was approved on the same day as you, yet your AOR was received over two weeks prior to mine.I don't think that's it. I'm applying as a German citizen (visa exempt) and I got it approved only on Sep 18 with a Jun 06 app received date. Some with mid/late June app received dates got it before me.
There seems to be about a 2-3 week window between the earliest and latest approvals for the same app received dates. Since your app was received in early July, you should probably give it another 1-3 weeks.
As to what causes these delays, I don't know. Probably something workflow related in how they divide up all the cases between their officers.
Edit: Also note that the time between receiving the app and AOR has gone down over the last few months from 6 weeks to 4 weeks. Work permit target processing times have remained pretty constant at 3-4 months. So for more recent applicants the wait between AOR and OWP approval might get a bit longer (because AORs are sent out quicker but won't actually speed up your OWP timeline).
Both of our OWPs were approved early according to the four month timescale IRCC quote, I’m also from a visa exempt country. This timescale of course is an average, a target, not a guarantee. I don’t think IRCC are concerned at all that someone may gets theirs a little earlier than someone who applied before that person. As long as the bulk of the OWPs are approved around the four month mark, they’re doing what they quoted they would.
A lot of us on here that received their OWPs in the last 4 weeks, have had their OWP approved around three to three and a half months after applying.