The Grenfell walkthrough is the worked case, and it does not locate one threshold.
Questions 1-2 are "partially crossed." Question 3 fails because resident fire-risk warnings did not enter the cladding sign-off. Questions 5-6 fail because complaint logs and fire-brigade letters existed and still bound nobody. Output: thresholds 2 and 3 both failed.
The claimed addition is a composition rule that identifies which kind of infrastructure to address first. Two broken links do not pick a first. A diagnostic that returns a pair is a list, not a locator.
"First" is the earliest break in the sequence, not a uniqueness contest.
Pain has to cross tacit-to-common, then common-to-record, then record-to-duty. If 2 and 3 are both down, you repair 2 first, because a duty with nothing admissible to attach to is empty. Grenfell's blogs and complaints are what make that order readable. The pair is the diagnosis. The sequence is the repair order.
That order only works if fixing the earlier link would let the later one fire.
Grenfell's threshold-3 claim is that no one bore cost for ignoring records that already existed — complaint logs, fire-brigade letters. Those are already past threshold 2. Putting fire-safety into the cladding sign-off does not create the missing duty for the files already on the shelf.
If threshold 3 is independently broken, "start at the earliest" is a slogan. The chain still stops at duty. You then need a rule for a later break that does not depend on the earlier one, not an instruction to start upstream.
The pair may be one miss counted twice.
Threshold 2 is: did the cognition enter a record that constrains the institution. Threshold 3 is: does that record trigger a duty. On Grenfell, the threshold-2 miss is "not in the cladding sign-off," and the threshold-3 miss is "other records didn't stop the cladding." Both are about the cladding decision not having to take the warnings.
If the binding record is defined as the one that would have stopped the works, failing to enter it is already a duty failure. Then "both failed in distinct ways" is one integration miss, recut. The composition rule has nothing extra to order.
Even if they are distinct, "address first" is a prediction.
Take the cladding decision as the object. Repair only the record link: resident fire-safety observations have to appear in the sign-off file in a form that can constrain the decision. Leave duty as described — no one pays for ignoring complaint logs.
If the sign-off still issues, repairing the record first was the wrong order and duty was doing the blocking. If the sign-off cannot issue once the warnings are in the file, record-first was real. Until one of those is named, "identify which to address first" is a caption on a pair.