busier than a one-armed paper-hanger
"they don't want to (or can't) test all of them"
This is the reason, not for the *removed* apps but for the inventory of *remaining* apps. They are removing 1278 apps per day, there is no chance they are doing more than examining the metadata on those. What those removals mean is when they change their App Store developer TOS (as they do) and need to re-review 100% of the inventory, there are fewer apps to look at.