Aside from the fact that ODJ&Co (or whoever owns it now) won’t penalize them for it, despite bylines being required in their contract, I can’t think of who will care that the bylines are being held. Do they think the audience will think that the WSJ’s got interns writing the articles? I can’t think of how this is an effective threat.
Reporters are very proud of their bylines. Giving them up voluntarily is a sign to management that the staff is ready to walk out.
It also just generally shows that the writers are pissed off.