possible bug: orphaned files left after immediate shutdown during DDL

Case:

  BEGIN;
  CREATE TABLE foo AS SELECT generate_series(1,1000);
  CHECKPOINT;
  SELECT relfilenode FROM pg_class WHERE relname='foo';

Let's say that returns 23456. Send the postmaster a SIGQUIT (immediate
shutdown), and then restart. The file 23456 is still in the filesystem,
but there's no record in pg_class for it. I don't see any obvious path
where it will be removed, so it looks like it will just stay there
forever.

My question is: is this a conscious decision to be paranoid during
recovery, or is this a bug? Or is there some reason that properly
determining which files should be removed at recovery time is
challenging?

Regards,
    Jeff Davis