How about describing what exactly taking full responsibility means for them in that particular situation?

Saying e.g. what is the impact on the situation for those responsible might be nice - no bonuses for next year? A plan in place so that this doesn't happen again? Stepping down as a CEO?

I mean, if I take responsibility for e.g. wrong tax filing, I pay the fine penalty, and/or go to jail.

Saying "I take responsibility" some kind of failure while having no consequences for said failure is not taking responsibility.