In a sense the criminal charges could well be unimportant here! Given that all of the tests on combustability have failed so far, it may simply be that there is no central responsibility. It may be, as May had it, that it has been a symptom of how we think of social housing but even that might not be clear since there haven't been tests on privately owned buildings yet.
If there is domed systemic failure in how we approach fire regulation, then MacConnell's metaphor is accurate and is the sort of rhetoric needed to keep the pressure on ensuring change. Is it helpful to determining what happened, no. Might it be helpful to keeping the pressure on avoiding this in the future, yes.