Genesis test failure: extra honest header download

```
$ git lg -1
99e49deff - (HEAD, origin/main, origin/HEAD) Add version `0.5` and its publishing date to the `utxo-db-api` doc (#1438) (21 hours ago)
$ cabal run ouroboros-consensus-diffusion:test:consensus-test -- --quickcheck-tests=1 --quickcheck-replay='(SMGen 5993563275997594115 6875817751050742035,0)' -p '/With some adversaries.honest peers do their own thing/' --quickcheck-shrinks=10000000
```

The test fails because the same header is downloaded from two honest peers, which CSJ is expected to avoid in the "idealized" scenario of these tests.

It wasn't obviously clear to me why it was happening in this case. But I've learned some things in in the other triage cases, and I have more suspicions now. This Issue is to return to this.

(This is not a blocker for the initial opt-in release of Genesis---it merely indicates the CSJ optimization is not a 100% optimal, which is harmless in the short-term.)

Re-run the supplied cabal command and QuickCheck case for “With some adversaries.honest peers do their own thing.” Trace the CSJ behavior in that test scenario to determine why two honest peers download the same header; done means the idealized test no longer observes that duplicate download, or the remaining limitation is documented and understood.

Written by the indexing model from the issue text.