“Three persons” fixes a number. “Three trustworthy persons” adds a qualification to that fixed number. If the original rule specifies only three, adding “trustworthy” is not a neutral paraphrase: it introduces a further condition requiring evidence.
The status of a specified number belongs to the discussion of particular wording, whereas the addition of a description concerns qualification. “All persons” raises a different issue of generality over a class.
The decisive question is not whether the extra condition seems sensible but whether the original provision or another authoritative proof establishes it. An attractive rationale is not itself sufficient legal evidence.