Why would it be large? Or problematically so.

Apple releases numbers: 130,000 app reviews per week.

The human component to this doesn't need to do much more than verify it works, they say they churn through that with just 500 reviewers that must be costing just a few $10s of millions.

They could certainly do a better job, but maybe that means 2,500 reviewers? That'd cost them half-a-year of Roblox's commissions.

If Google needs 2x as many that's 5,000 people, their whole Roblox commission. There are more people working at their HQ, and this is a job they can distribute between cheaper countries.

And they could reasonably have different tiers/levels of review triggered by use. A fairly basic automatic review, until you get 10 installs. Then something more complex, up to 1000 installs, etc.