Ooh, I was so hoping someone would take up the challenge! This is a far shorter answer than I had honestly thought was possible. More readable too, somehow? Great use of tee that I would never have come up with (though I hear what you say about there maybe not being ordering guarantees).

Unfortunately, it's not 100% correct, due to misaligned headers:

  REPOSITORY TAG IMAGE ID CREATED SIZE
  registry.fedoraproject.org/fedora-toolbox 44 5a36f433c691 2 months ago 2.14 GB
  quay.io/keycloak/keycloak latest 1361d6e49205 9 days ago 478 MB
  ...

I think that speaks to your final point, which is spot-on:

> I'd probably just end up dropping the header and living with worse output in reality

This pretty much sums up plain text and unix shell imo. It's very much the pragmatic solution here, and it's what ~100% of shell scripters would choose to do. And it should make anyone question the orthodoxy around the "power" of plain text in shells.