JS #277 has the gist of the issue.
Without actually knowing what the crew saw, or think that they saw, we should not cite deviation from the norm (poor discipline) as a conclusion.
Furthermore if we were to question what good discipline is, or what constitutes discipline, I suspect that there would be many lengthy ‘CRM’ type answers, dependant on cross - crew ‘monitoring’ and call outs; but most would overlook erroneous or illusionary instances where both crew could have the same situational awareness.
The safety problem is to identify these situations beforehand, thinking about ‘what - if’, with regular updating from incidents and accidents; the endless process of learning.