Apple has responded
Engineering has determined that your bug report (31397880) is a duplicate of another issue (26394372) and will be closed.
The open or closed status of the original bug report your issue was duplicated to appears in the yellow "Duplicate of XXXXXXXX" section of the bug reporter user interface. This section appears near the top of the right column's bug detail view just under the bug number, title, state, product and rank.
An example of the duplicate section from the bug reporter user interface with your bug and the duplicate bug info is included below:
31397880 After upgrading to 10.12.4 window content on external monitors is garbled
State: Closed Product:
Rank: No Value
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Duplicate of 26394372 (Open or Closed; log in to see the actual state)
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