I about gave myself an aneurysm deliberately and pedantically (and dare I say, facetiously) trying to parse this as written (lack of punctuation) rather than as intended.

Any such pain is well deserved, of course, but still.

Best guess, something owns or has some oversight of an entire group of human (or at least sentient) control tests (or control testers) that are identified by the letter ‘a’.

There is no conclusive evidence that its b control test people are better than its a control test people.