Most of the things i had to fix came by order of the CEO directly. If the new colleagues will not learn within a due time frame, i am guessing their carreer might take a bump.
Personally i don't really mind at the moment. I get to do various work and it's been less stressful.
Only if the Peter Principal is in effect. As a manager they would be uniquely positioned to scope and assess the prep work. With a bit of mentoring they might "get it" sooner, rather than "eventually".
I have a coworker that placed a "return true" at the beginning of a failing test, and when I reverted the change spent ONE ENTIRE MONTH arguing that I had broken the test and it was now my responsibility to fix it. Several emails per day, because according to him what he did is completely legit.
He was at my same level then. Now he's 2 levels higher.
Personally i don't really mind at the moment. I get to do various work and it's been less stressful.