One case of incomplete filters we’ve run into is calexps written before w_2021_06, which updated most tasks to use FilterLabel internally (as described in afw.image.Filter is now deprecated). Though the Exposure format for these files used FilterLabel, these labels were populated using old-style Filter code, and therefore kept the old behavior of being identified only by their band.
This should not be a major problem in Gen 2, as these files can be patched on read following DM-27178; a Gen 3 fix is pending on DM-28583.