Pins the reason the exclusion matches the marker's VALUE against the parent id instead
of its presence: a continuation copies model_config verbatim, so a `_branched_from`
marker rides along. A presence check (#116377's variant) would leave the continuation
unroutable — exactly the shape this test fails on against that branch.
Salvages #109699 (@Lei-k). Supersedes #116377 (@strzhao).
Co-authored-by: strzhao <strzhao@users.noreply.github.com>
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