Is “+81H DAYS” a plaintext leak?

[sjmurdoch]

One payload in the corpus ends in a legible English word. PRN 6 transmitted it twice on 18 July 2019, at 00:10:48 and 00:23:18 UTC:

+'X1D8A°PTA9F+81H DAYS

It is a genuine broadcast. Both observations pass the Words 2–10 LNAV parity chain under the D30* interpretation (chance pass ≈ 2^–54) and were recorded bit-identically by seven independent ground stations (multiplicity = 7). It is a single-day rotation transient: it occupies two consecutive Page 17 slots between the outgoing and incoming daily messages, aired for roughly twenty-five minutes, and was never transmitted again on any satellite.

2019-07-17 23:58:18   B67+D3UFB0NBXK°CCB8/VI   outgoing daily message
2019-07-18 00:10:48   +'X1D8A°PTA9F+81H DAYS   transient
2019-07-18 00:23:18   +'X1D8A°PTA9F+81H DAYS
2019-07-18 00:35:48   FZPYXNQ+QTJX5-M555NK82   incoming daily message

The readable run is likely just to be one of the corpus's expected letter-run coincidences. Of the 5,009 unique payloads, 3,536 contain a run of four or more consecutive letters, 2,245 a run of five or more, and 1,305 a run of six or more. A dictionary scan against a character-shuffled null returns 163 four-letter hits against ~113 expected — the surplus fully accounted for by the 55 literal TEXT prefixes — five five-letter hits against 3.9, and zero of six letters or more. DAYS is one of those 163 four-letter hits. The payload's entropy is 3.88 bits per character against a corpus mean of 4.03, the readable run sits alone at the tail of an otherwise high-entropy string, and 81H is non-lexical.

duckdb -readonly data/messages.duckdb -c "
  SELECT DISTINCT ascii_message, ROUND(entropy,2) AS H
  FROM special_messages WHERE regexp_matches(ascii_message,'[A-Z]{4,}') ORDER BY entropy"

On this evidence 81H DAYS is a real broadcast whose single readable word falls within the corpus's chance letter-run yield, indistinguishable in entropy and structure from the ciphertext around it. The only deliberate plaintext the archive contains appears to be the TEXT prefix. What, if anything, to make of the coincidence is left to the reader.