Naming is bad and confusing, but the 'expander' code path from readfile
can also be used outside of the reading context (see e.g.
`BKE_blendfile_write_partial` code). So code cannot assume that it is
exclusively working on data freshly read from file.
This should be renamed - but should also be probably replaced by
proper usage of the more generic 'foreach_id' code anyway, see #105134.
Found while investigating #109588.
e1b1b2a8b4