Yeah I did some googling and it seemed to indicate the reviewers are actually at Apple... with the scale of work I would expect they were not / be someplace cheaper.
Re:App Review process updates
by carstenhag on Monday August 31, 2020 @05:00PM
(#24335887)
Could sti be hired at Apple directly, but at another city/country with cheap wage costs. No clue though where they have their employees.
It's probably exacerbated by the lack of sideloading and alternate app stores on the platform.